Type: Package
Title: Dictionary-Based Sentiment Analysis
Version: 1.3-5
Date: 2023-08-23
Description: Performs a sentiment analysis of textual contents in R. This implementation utilizes various existing dictionaries, such as Harvard IV, or finance-specific dictionaries. Furthermore, it can also create customized dictionaries. The latter uses LASSO regularization as a statistical approach to select relevant terms based on an exogenous response variable.
License: MIT + file LICENSE
URL: https://github.com/sfeuerriegel/SentimentAnalysis
BugReports: https://github.com/sfeuerriegel/SentimentAnalysis/issues
Depends: R (≥ 2.10)
Imports: tm (≥ 0.6), qdapDictionaries, ngramrr (≥ 0.1), moments, stringdist, glmnet, spikeslab (≥ 1.1), ggplot2
Suggests: testthat, knitr, rmarkdown, SnowballC, XML, mgcv
LazyData: true
Encoding: UTF-8
RoxygenNote: 7.2.3
VignetteBuilder: knitr
NeedsCompilation: no
Packaged: 2023-08-23 19:43:52 UTC; nproe
Author: Nicolas Proellochs [aut, cre], Stefan Feuerriegel [aut]
Maintainer: Nicolas Proellochs <nicolas@nproellochs.com>
Repository: CRAN
Date/Publication: 2023-08-23 20:10:03 UTC

SentimentAnalysis: A package for analyzing sentiment of texts

Description

The SentimentAnalysis package provides routines to quickly measure the sentiment of written materials. It ships a dedicated class SentimentDictionary to store different variants of dictionaries (including pre-built ones that are ready to go) and helps the user with routines for constructing domain-specific dictionaries and evaluating the performance of common rules for analyzing sentiment.

Author(s)

Maintainer: Nicolas Proellochs nicolas@nproellochs.com

Authors:

See Also

Useful links:

Dictionary with opinionated words from the Harvard-IV dictionary as used in the General Inquirer software

Description

Dictionary with a list of positive and negative words according to the psychological Harvard-IV dictionary as used in the General Inquirer software. This is a general-purpose dictionary developed by the Harvard University.

Usage

data(DictionaryGI)

Format

A list with different terms according to Henry

Note

All words are in lower case and non-stemmed

Source

https://inquirer.sites.fas.harvard.edu/homecat.htm

Examples

data(DictionaryGI)
summary(DictionaryGI)

Dictionary with opinionated words from Henry's Financial dictionary

Description

Dictionary with a list of positive and negative words according to the Henry's finance-specific dictionary. This dictionary was first presented in the Journal of Business Communication among one of the early adopters of text analysis in the finance discipline.

Usage

data(DictionaryHE)

Format

A list with different wordlists according to Henry

Note

All words are in lower case and non-stemmed

References

Henry (2008): Are Investors Influenced By How Earnings Press Releases Are Written?, Journal of Business Communication, 45:4, 363-407

Examples

data(DictionaryHE)
summary(DictionaryHE)

Dictionary with opinionated words from Loughran-McDonald Financial dictionary

Description

Dictionary with a list of positive, negative and uncertainty words according to the Loughran-McDonald finance-specific dictionary. This dictionary was first presented in the Journal of Finance and has been widely used in the finance domain ever since.

Usage

data(DictionaryLM)

Format

A list with different terms according to Loughran-McDonald

Note

All words are in lower case and non-stemmed

Source

https://sraf.nd.edu/loughranmcdonald-master-dictionary/

References

Loughran and McDonald (2011) When is a Liability not a Liability? Textual Analysis, Dictionaries, and 10-Ks, Journal of Finance, 66:1, 35-65

Examples

data(DictionaryLM)
summary(DictionaryLM)

Create new sentiment dictionary based on input

Description

Depending on the input, this function creates a new sentiment dictionary of different type.

Usage

SentimentDictionary(...)

Arguments

...

Arguments as passed to one of the three functions SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

See Also

SentimentDictionaryWordlist, SentimentDictionaryBinary, SentimentDictionaryWeighted

Create a sentiment dictionary of positive and negative words

Description

This routines creates a new object of type SentimentDictionaryBinary that stores two separate vectors of negative and positive words

Usage

SentimentDictionaryBinary(positiveWords, negativeWords)

Arguments

positiveWords

is a vector containing the entries labeled as positive

negativeWords

is a vector containing the entries labeled as negative

Value

Returns a new object of type SentimentDictionaryBinary

See Also

SentimentDictionary

Examples

# generate a dictionary with positive and negative words
d <- SentimentDictionaryBinary(c("increase", "rise", "more"),
                               c("fall", "drop"))
summary(d)
# alternative call
d <- SentimentDictionary(c("increase", "rise", "more"),
                         c("fall", "drop"))
summary(d)

Create a sentiment dictionary of words linked to a score

Description

This routine creates a new object of type SentimentDictionaryWeighted that contains a number of words, each linked to a continuous score (i.e. weight) for specifying its polarity. The scores can later be interpreted as a linear model

Usage

SentimentDictionaryWeighted(
  words,
  scores,
  idf = rep(1, length(words)),
  intercept = 0
)

Arguments

words

is collection (vector) of different words as strings

scores

are the corresponding scores or weights denoting the word's polarity

idf

provide further details on the frequency of words in the corpus as an additional source for normalization

intercept

is an optional parameter for shifting the zero level (default: 0)

Value

Returns a new object of type SentimentDictionaryWordlist

Note

The intercept is useful when the mean or median of a response variable is not exactly located at zero. For instance, stock market returns have slight positive bias.

Source

doi:10.1371/journal.pone.0209323

References

Pr\"ollochs and Feuerriegel (2018). Statistical inferences for Polarity Identification in Natural Language, PloS One 13(12).

See Also

SentimentDictionary

Examples

# generate dictionary (based on linear model)
d <- SentimentDictionaryWeighted(c("increase", "decrease", "exit"),
                                 c(+1, -1, -10),
                                 rep(NA, 3))
summary(d)
# alternative call
d <- SentimentDictionaryWeighted(c("increase", "decrease", "exit"),
                                 c(+1, -1, -10))
summary(d)
# alternative call
d <- SentimentDictionary(c("increase", "decrease", "exit"),
                         c(+1, -1, -10),
                         rep(NA, 3))
summary(d)

Create a sentiment dictionary consisting of a simple wordlist

Description

This routine creates a new object of type SentimentDictionaryWordlist

Usage

SentimentDictionaryWordlist(wordlist)

Arguments

wordlist

is a vector containing the individual entries as strings

Value

Returns a new object of type SentimentDictionaryWordlist

See Also

SentimentDictionary

Examples

# generate a dictionary with "uncertainty" words
d <- SentimentDictionaryWordlist(c("uncertain", "possible", "likely"))
summary(d)
# alternative call
d <- SentimentDictionary(c("uncertain", "possible", "likely"))
summary(d)

Sentiment analysis

Description

Performs sentiment analysis of given object (vector of strings, document-term matrix, corpus).

Usage

analyzeSentiment(
  x,
  language = "english",
  aggregate = NULL,
  rules = defaultSentimentRules(),
  removeStopwords = TRUE,
  stemming = TRUE,
  ...
)

## S3 method for class 'Corpus'
analyzeSentiment(
  x,
  language = "english",
  aggregate = NULL,
  rules = defaultSentimentRules(),
  removeStopwords = TRUE,
  stemming = TRUE,
  ...
)

## S3 method for class 'character'
analyzeSentiment(
  x,
  language = "english",
  aggregate = NULL,
  rules = defaultSentimentRules(),
  removeStopwords = TRUE,
  stemming = TRUE,
  ...
)

## S3 method for class 'data.frame'
analyzeSentiment(
  x,
  language = "english",
  aggregate = NULL,
  rules = defaultSentimentRules(),
  removeStopwords = TRUE,
  stemming = TRUE,
  ...
)

## S3 method for class 'TermDocumentMatrix'
analyzeSentiment(
  x,
  language = "english",
  aggregate = NULL,
  rules = defaultSentimentRules(),
  removeStopwords = TRUE,
  stemming = TRUE,
  ...
)

## S3 method for class 'DocumentTermMatrix'
analyzeSentiment(
  x,
  language = "english",
  aggregate = NULL,
  rules = defaultSentimentRules(),
  removeStopwords = TRUE,
  stemming = TRUE,
  ...
)

Arguments

x

A vector of characters, a data.frame, an object of type Corpus, TermDocumentMatrix or DocumentTermMatrix

language

Language used for preprocessing operations (default: English)

aggregate

A factor variable by which documents can be grouped. This helpful when joining e.g. news from the same day or move reviews by the same author

rules

A named list containing individual sentiment metrics. Therefore, each entry consists itself of a list with first a method, followed by an optional dictionary.

removeStopwords

Flag indicating whether to remove stopwords or not (default: yes)

stemming

Perform stemming (default: TRUE)

...

Additional parameters passed to function for e.g. preprocessing

Details

This function returns a data.frame with continuous values. If one desires other formats, one needs to convert these. Common examples of such formats are binary response values (positive / negative) or tertiary (positive, neutral, negative). Hence, consider using the functions convertToBinaryResponse and convertToDirection, which can convert a vector of continuous sentiment scores into a factor object.

Value

Result is a matrix with sentiment values for each document across all defined rules

See Also

compareToResponse for evaluating the results, convertToBinaryResponse and convertToDirection for for getting binary results, generateDictionary for dictionary generation, plotSentiment and plotSentimentResponse for visualization

Examples

## Not run: 
library(tm)

# via vector of strings
corpus <- c("Positive text", "Neutral but uncertain text", "Negative text")
sentiment <- analyzeSentiment(corpus)
compareToResponse(sentiment, c(+1, 0, -2))

# via Corpus from tm package
data("crude")
sentiment <- analyzeSentiment(crude)
    
# via DocumentTermMatrix (with stemmed entries)
dtm <- DocumentTermMatrix(VCorpus(VectorSource(c("posit posit", "negat neutral")))) 
sentiment <- analyzeSentiment(dtm)
compareToResponse(sentiment, convertToBinaryResponse(c(+1, -1)))

# By adapting the parameter rules, one can incorporate customized dictionaries
# e.g. in order to adapt to arbitrary languages
dictionaryAmplifiers <- SentimentDictionary(c("more", "much"))
sentiment <- analyzeSentiment(corpus,
                              rules=list("Amplifiers"=list(ruleRatio,
                                                           dictionaryAmplifiers)))
                                                           
# On can also restrict the number of computed methods to the ones of interest
# in order to achieve performance optimizations
sentiment <- analyzeSentiment(corpus,
                              rules=list("SentimentLM"=list(ruleSentiment, 
                                                            loadDictionaryLM())))
sentiment

## End(Not run)

Compares two dictionaries

Description

Routine compares two dictionaries in terms of how similarities and differences. Among the calculated measures are the total of distinct words, the overlap between both dictionaries, etc.

Usage

compareDictionaries(d1, d2)

Arguments

d1

is the first sentiment dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

d2

is the first sentiment dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

Value

Returns list with different metrics depending on dictionary type

Note

Currently, this routine only supports the case where both dictionaries are of the same type

See Also

SentimentDictionaryWordlist, SentimentDictionaryBinary, SentimentDictionaryWeighted for the specific classes

Examples

d1 <- SentimentDictionary(c("uncertain", "possible", "likely"))
d2 <- SentimentDictionary(c("rather", "intend", "likely"))
cmp <- compareDictionaries(d1, d2)

d1 <- SentimentDictionary(c("increase", "rise", "more"),
                          c("fall", "drop"))
d2 <- SentimentDictionary(c("positive", "rise", "more"),
                          c("negative", "drop"))
cmp <- compareDictionaries(d1, d2)

d1 <- SentimentDictionary(c("increase", "decrease", "exit"),
                          c(+1, -1, -10),
                          rep(NA, 3))
d2 <- SentimentDictionary(c("increase", "decrease", "drop", "neutral"),
                          c(+2, -5, -1, 0),
                          rep(NA, 4))
cmp <- compareDictionaries(d1, d2)

Compare sentiment values to existing response variable

Description

This function compares the calculated sentiment values with an external response variable. Examples of such an exogenous response are stock market movements or IMDb move rating. Both usually reflect a "true" value that the sentiment should match.

Usage

compareToResponse(sentiment, response)

## S3 method for class 'logical'
compareToResponse(sentiment, response)

## S3 method for class 'factor'
compareToResponse(sentiment, response)

## S3 method for class 'integer'
compareToResponse(sentiment, response)

## S3 method for class 'data.frame'
compareToResponse(sentiment, response)

## S3 method for class 'numeric'
compareToResponse(sentiment, response)

Arguments

sentiment

Matrix with sentiment scores for each document across several sentiment rules

response

Vector with "true" response. This vector can either be of a continuous numeric or binary values. In case of the latter, FALSE is matched to a negative sentiment value, while TRUE is matched to a non-negative one.

Value

Matrix with different performance metrics for all given sentiment rules

Examples

sentiment <- matrix(c(5.5, 2.9, 0.9, -1), 
                    dimnames=list(c("A", "B", "C", "D"), c("Sentiment")))

# continuous numeric response variable
response <- c(5, 3, 1, -1)
compareToResponse(sentiment, response)

# binary response variable
response <- c(TRUE, TRUE, FALSE, FALSE)
compareToResponse(sentiment, response)

Convert continuous sentiment to direction

Description

This function converts continuous sentiment scores into a their corresponding binary sentiment class. As such, the result is a factor with two levels indicating positive and negative content. Neutral documents (with a sentiment score of 0) are counted as positive.

Usage

convertToBinaryResponse(sentiment)

Arguments

sentiment

Vector, matrix or data.frame with sentiment scores.

Details

If a matrix or data.frame is provided, this routine does not touch all columns. In fact, it scans for those where the column name starts with "Sentiment" and changes these columns only. Hence, columns with pure negativity, positivity or ratios or word counts are ignored.

Value

If a vector is supplied, it returns a factor with two levels representing positive and negative content. Otherwise, it returns a data.frame with the corresponding columns being exchanged.

See Also

convertToDirection

Examples

sentiment <- c(-1, -0.5, +1, 0.6, 0)
convertToBinaryResponse(sentiment)
convertToDirection(sentiment)

df <- data.frame(No=1:5, Sentiment=sentiment)
df
convertToBinaryResponse(df)
convertToDirection(df)

Convert continuous sentiment to direction

Description

This function converts continuous sentiment scores into a their corresponding sentiment direction. As such, the result is a factor with three levels indicating positive, neutral and negative content. In contrast to convertToBinaryResponse, neutral documents have their own category.

Usage

convertToDirection(sentiment)

Arguments

sentiment

Vector, matrix or data.frame with sentiment scores.

Details

If a matrix or data.frame is provided, this routine does not touch all columns. In fact, it scans for those where the column name starts with "Sentiment" and changes these columns only. Hence, columns with pure negativity, positivity or ratios or word counts are ignored.

Value

If a vector is supplied, it returns a factor with three levels representing positive, neutral and negative content. Otherwise, it returns a data.frame with the corresponding columns being exchanged.

See Also

convertToBinaryResponse

Examples

sentiment <- c(-1, -0.5, +1, 0.6, 0)
convertToBinaryResponse(sentiment)
convertToDirection(sentiment)

df <- data.frame(No=1:5, Sentiment=sentiment)
df
convertToBinaryResponse(df)
convertToDirection(df)

Count words

Description

Function counts the words in each document

Usage

countWords(
  x,
  aggregate = NULL,
  removeStopwords = TRUE,
  language = "english",
  ...
)

## S3 method for class 'Corpus'
countWords(
  x,
  aggregate = NULL,
  removeStopwords = TRUE,
  language = "english",
  ...
)

## S3 method for class 'character'
countWords(
  x,
  aggregate = NULL,
  removeStopwords = TRUE,
  language = "english",
  ...
)

## S3 method for class 'data.frame'
countWords(
  x,
  aggregate = NULL,
  removeStopwords = TRUE,
  language = "english",
  ...
)

## S3 method for class 'TermDocumentMatrix'
countWords(
  x,
  aggregate = NULL,
  removeStopwords = TRUE,
  language = "english",
  ...
)

## S3 method for class 'DocumentTermMatrix'
countWords(
  x,
  aggregate = NULL,
  removeStopwords = TRUE,
  language = "english",
  ...
)

Arguments

x

A vector of characters, a data.frame, an object of type Corpus, TermDocumentMatrix or DocumentTermMatrix

aggregate

A factor variable by which documents can be grouped. This helpful when joining e.g. news from the same day or move reviews by the same author

removeStopwords

Flag indicating whether to remove stopwords or not (default: yes)

language

Language used for preprocessing operations (default: English)

...

Additional parameters passed to function for e.g. preprocessing

Value

Result is a matrix with word counts for each document across

Examples

documents <- c("This is a test", "an one more")

# count words (without stopwords)
countWords(documents)

# count all words (including stopwords)
countWords(documents, removeStopwords=FALSE)

Elastic net estimation

Description

Function estimates coefficients based on elastic net regularization.

Usage

enetEstimation(
  x,
  response,
  control = list(alpha = 0.5, s = "lambda.min", family = "gaussian", grouped = FALSE),
  ...
)

Arguments

x

An object of type DocumentTermMatrix.

response

Response variable including the given gold standard.

control

(optional) A list of parameters defining the model as follows:

  • "alpha"Abstraction parameter for switching between LASSO and ridge regularization (with default alpha=0.5). Best option is to loop over this parameter and test different alternatives.

  • "s"Value of the parameter lambda at which the elastic net is evaluated. Default is s="lambda.1se" which takes the calculated minimum value for \lambda and then subtracts one standard error in order to avoid overfitting. This often results in a better performance than using the minimum value itself given by lambda="lambda.min".

  • "family"Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glmnet for further details.

  • "grouped" Determines whether grouped function is used (with default FALSE).

...

Additional parameters passed to function for glmnet.

Value

Result is a list with coefficients, coefficient names and the model intercept.

Extract words from dictionary

Description

Returns all entries from a dictionary.

Usage

extractWords(d)

Arguments

d

Dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

Examples

extractWords(SentimentDictionary(c("uncertain", "possible", "likely"))) # returns 3
extractWords(SentimentDictionary(c("increase", "rise", "more"),
                                 c("fall", "drop"))) # returns 5
extractWords(SentimentDictionary(c("increase", "decrease", "exit"),
                                 c(+1, -1, -10),
                                 rep(NA, 3))) # returns 3

Generates dictionary of decisive terms

Description

Routine applies method for dictionary generation (LASSO, ridge regularization, elastic net, ordinary least squares, generalized linear model or spike-and-slab regression) to the document-term matrix in order to extract decisive terms that have a statistically significant impact on the response variable.

Usage

generateDictionary(
  x,
  response,
  language = "english",
  modelType = "lasso",
  filterTerms = NULL,
  control = list(),
  minWordLength = 3,
  sparsity = 0.9,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

## S3 method for class 'Corpus'
generateDictionary(
  x,
  response,
  language = "english",
  modelType = "lasso",
  filterTerms = NULL,
  control = list(),
  minWordLength = 3,
  sparsity = 0.9,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

## S3 method for class 'character'
generateDictionary(
  x,
  response,
  language = "english",
  modelType = "lasso",
  filterTerms = NULL,
  control = list(),
  minWordLength = 3,
  sparsity = 0.9,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

## S3 method for class 'data.frame'
generateDictionary(
  x,
  response,
  language = "english",
  modelType = "lasso",
  filterTerms = NULL,
  control = list(),
  minWordLength = 3,
  sparsity = 0.9,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

## S3 method for class 'TermDocumentMatrix'
generateDictionary(
  x,
  response,
  language = "english",
  modelType = "lasso",
  filterTerms = NULL,
  control = list(),
  minWordLength = 3,
  sparsity = 0.9,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

## S3 method for class 'DocumentTermMatrix'
generateDictionary(
  x,
  response,
  language = "english",
  modelType = "lasso",
  filterTerms = NULL,
  control = list(),
  minWordLength = 3,
  sparsity = 0.9,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

Arguments

x

A vector of characters, a data.frame, an object of type Corpus, TermDocumentMatrix or DocumentTermMatrix.

response

Response variable including the given gold standard.

language

Language used for preprocessing operations (default: English).

modelType

A string denoting the estimation method. Allowed values are lasso, ridge, enet, lm or glm or spikeslab.

filterTerms

Optional vector of strings (default: NULL) to filter terms that are used for dictionary generation.

control

(optional) A list of parameters defining the model used for dictionary generation.

If modelType=lasso is selected, individual parameters are as follows:

  • "s" Value of the parameter lambda at which the LASSO is evaluated. Default is s="lambda.1se" which takes the calculated minimum value for \lambda and then subtracts one standard error in order to avoid overfitting. This often results in a better performance than using the minimum value itself given by lambda="lambda.min".

  • "family" Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glmnet for further details.

  • "grouped" Determines whether grouped LASSO is used (with default FALSE).

If modelType=ridge is selected, individual parameters are as follows:

  • "s" Value of the parameter lambda at which the ridge is evaluated. Default is s="lambda.1se" which takes the calculated minimum value for \lambda and then subtracts one standard error in order to avoid overfitting. This often results in a better performance than using the minimum value itself given by lambda="lambda.min".

  • "family" Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glmnet for further details.

  • "grouped" Determines whether grouped function is used (with default FALSE).

If modelType=enet is selected, individual parameters are as follows:

  • "alpha" Abstraction parameter for switching between LASSO (with alpha=1) and ridge regression (alpha=0). Default is alpha=0.5. Recommended option is to test different values between 0 and 1.

  • "s" Value of the parameter lambda at which the elastic net is evaluated. Default is s="lambda.1se" which takes the calculated minimum value for \lambda and then subtracts one standard error in order to avoid overfitting. This often results in a better performance than using the minimum value itself given by lambda="lambda.min".

  • "family" Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glmnet for further details.

  • "grouped" Determines whether grouped function is used (with default FALSE).

If modelType=lm is selected, no parameters are passed on.

If modelType=glm is selected, individual parameters are as follows:

  • "family" Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glm for further details.

If modelType=spikeslab is selected, individual parameters are as follows:

  • "n.iter1" Number of burn-in Gibbs sampled values (i.e., discarded values). Default is 500.

  • "n.iter2" Number of Gibbs sampled values, following burn-in. Default is 500.

minWordLength

Removes words given a specific minimum length (default: 3). This preprocessing is applied when the input is a character vector or a corpus and the document-term matrix is generated inside the routine.

sparsity

A numeric for removing sparse terms in the document-term matrix. The argument sparsity specifies the maximal allowed sparsity. Default is sparsity=0.9, however, this is only applied when the document-term matrix is calculated inside the routine.

weighting

Weights a document-term matrix by e.g. term frequency - inverse document frequency (default). Other variants can be used from DocumentTermMatrix.

...

Additional parameters passed to function for e.g. preprocessing or glmnet.

Value

Result is a matrix which sentiment values for each document across all defined rules

Source

doi:10.1371/journal.pone.0209323

References

Pr\"ollochs and Feuerriegel (2018). Statistical inferences for Polarity Identification in Natural Language, PloS One 13(12).

See Also

analyzeSentiment, predict.SentimentDictionaryWeighted, plot.SentimentDictionaryWeighted and compareToResponse for advanced evaluations

Examples

# Create a vector of strings
documents <- c("This is a good thing!",
               "This is a very good thing!",
               "This is okay.",
               "This is a bad thing.",
               "This is a very bad thing.")
response <- c(1, 0.5, 0, -0.5, -1)

# Generate dictionary with LASSO regularization
dictionary <- generateDictionary(documents, response)

# Show dictionary
dictionary
summary(dictionary)
plot(dictionary)

# Compute in-sample performance
sentiment <- predict(dictionary, documents)
compareToResponse(sentiment, response)
plotSentimentResponse(sentiment, response)

# Generate new dictionary with spike-and-slab regression instead of LASSO regularization
library(spikeslab)
dictionary <- generateDictionary(documents, response, modelType="spikeslab")

# Generate new dictionary with tf weighting instead of tf-idf

library(tm)
dictionary <- generateDictionary(documents, response, weighting=weightTf)
sentiment <- predict(dictionary, documents)
compareToResponse(sentiment, response)

# Use instead lambda.min from the LASSO estimation
dictionary <- generateDictionary(documents, response, control=list(s="lambda.min"))
sentiment <- predict(dictionary, documents)
compareToResponse(sentiment, response)

# Use instead OLS as estimation method
dictionary <- generateDictionary(documents, response, modelType="lm")
sentiment <- predict(dictionary, documents)
sentiment

dictionary <- generateDictionary(documents, response, modelType="lm", 
                                 filterTerms = c("good", "bad"))
sentiment <- predict(dictionary, documents)
sentiment

dictionary <- generateDictionary(documents, response, modelType="lm", 
                                 filterTerms = extractWords(loadDictionaryGI()))
sentiment <- predict(dictionary, documents)
sentiment

# Generate dictionary without LASSO intercept
dictionary <- generateDictionary(documents, response, intercept=FALSE)
dictionary$intercept
 
## Not run: 
imdb <- loadImdb()

# Generate Dictionary
dictionary_imdb <- generateDictionary(imdb$Corpus, imdb$Rating, family="poisson")
summary(dictionary_imdb)

compareDictionaries(dictionary_imdb,
                    loadDictionaryGI())
                    
# Show estimated coefficients with Kernel Density Estimation (KDE)
plot(dictionary_imdb)
plot(dictionary_imdb) + xlim(c(-0.1, 0.1))

# Compute in-sample performance
pred_sentiment <- predict(dict_imdb, imdb$Corpus)
compareToResponse(pred_sentiment, imdb$Rating)

# Test a different sparsity parameter
dictionary_imdb <- generateDictionary(imdb$Corpus, imdb$Rating, family="poisson", sparsity=0.99)
summary(dictionary_imdb)
pred_sentiment <- predict(dict_imdb, imdb$Corpus)
compareToResponse(pred_sentiment, imdb$Rating)

## End(Not run)

Estimation via generalized least squares

Description

Function estimates coefficients based on generalized least squares.

Usage

glmEstimation(x, response, control = list(family = "gaussian"), ...)

Arguments

x

An object of type DocumentTermMatrix.

response

Response variable including the given gold standard.

control

(optional) A list of parameters defining the model as follows:

  • "family"Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glm for further details.

...

Additional parameters passed to function for glm.

Value

Result is a list with coefficients, coefficient names and the model intercept.

Result is a list with coefficients, coefficient names and the model intercept.

Lasso estimation

Description

Function estimates coefficients based on LASSO regularization.

Usage

lassoEstimation(
  x,
  response,
  control = list(alpha = 1, s = "lambda.min", family = "gaussian", grouped = FALSE),
  ...
)

Arguments

x

An object of type DocumentTermMatrix.

response

Response variable including the given gold standard.

control

(optional) A list of parameters defining the LASSO model as follows:

  • "s"Value of the parameter lambda at which the LASSO is evaluated. Default is s="lambda.1se" which takes the calculated minimum value for \lambda and then subtracts one standard error in order to avoid overfitting. This often results in a better performance than using the minimum value itself given by lambda="lambda.min".

  • "family"Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glmnet for further details.

  • "grouped" Determines whether grouped LASSO is used (with default FALSE).

...

Additional parameters passed to function for glmnet.

Value

Result is a list with coefficients, coefficient names and the model intercept.

Ordinary least squares estimation

Description

Function estimates coefficients based on ordinary least squares.

Usage

lmEstimation(x, response, control = list(), ...)

Arguments

x

An object of type DocumentTermMatrix.

response

Response variable including the given gold standard.

control

(optional) A list of parameters (not used).

...

Additional parameters (not used).

Value

Result is a list with coefficients, coefficient names and the model intercept.

Loads Harvard-IV dictionary into object

Description

Loads Harvard-IV dictionary (as used in General Inquirer) into a standardized dictionary object

Usage

loadDictionaryGI()

Value

object of class SentimentDictionary

Note

Result is a list of stemmed words in lower case

Loads Henry's finance-specific dictionary into object

Description

Loads Henry's finance-specific dictionary into a standardized dictionary object

Usage

loadDictionaryHE()

Value

object of class SentimentDictionary

Note

Result is a list of stemmed words in lower case

Loads Loughran-McDonald dictionary into object

Description

Loads Loughran-McDonald financial dictionary into a standardized dictionary object (here, categories positive and negative are considered)

Usage

loadDictionaryLM()

Value

object of class SentimentDictionary

Note

Result is a list of stemmed words in lower case

Loads uncertainty words from Loughran-McDonald into object

Description

Loads uncertainty words from Loughran-McDonald into a standardized dictionary object

Usage

loadDictionaryLM_Uncertainty()

Value

object of class SentimentDictionary

Note

Result is a list of stemmed words in lower case

Loads polarity words from qdap package into object

Description

Loads polarity words from data object key.pol which is by the package qdap. This is then converted into a standardized dictionary object

Usage

loadDictionaryQDAP()

Value

object of class SentimentDictionary

Note

Result is a list of stemmed words in lower case

Source

https://www.cs.uic.edu/~liub/FBS/sentiment-analysis.html

References

Hu and Liu (2004). Mining Opinion Features in Customer Reviews. National Conference on Artificial Intelligence.

Retrieves IMDb dataset

Description

Function downloads IMDb dataset and prepares corresponding user ratings for easy usage.

Usage

loadImdb()

Value

Returns a list where entry named Corpus contains the IMDb reviews, and Rating is the corresponding scaled rating.

References

Pang and Lee (2015) Seeing Stars: Exploiting Class Relationships for Sentiment Categorization with Respect to Rating Scales, Proceeding of the ACL. See http://www.cs.cornell.edu/people/pabo/movie-review-data/

Examples

## Not run: 
imdb <- loadImdb()
dictionary <- generateDictionary(imdb$Corpus, imdb$Rating)

## End(Not run)

Estimation method

Description

Decides upon a estimation method for dictionary generation. Input is a name for the estimation method, output is the corresponding function object.

Usage

lookupEstimationMethod(type)

Arguments

type

A string denoting the estimation method. Allowed values are lasso, ridge, enet, lm, glm or spikeslab.

Value

Function that implements the specific estimation method.

N-gram tokenizer

Description

A tokenizer for use with a document-term matrix from the tm package. Supports both character and word ngrams, including own wrapper to handle non-Latin encodings

Usage

ngram_tokenize(x, char = FALSE, ngmin = 1, ngmax = 3)

Arguments

x

input string

char

boolean value specifying whether to use character (char = TRUE) or word n-grams (char = FALSE, default)

ngmin

integer giving the minimum order of n-gram (default: 1)

ngmax

integer giving the maximum order of n-gram (default: 3)

Examples

library(tm)
en <- c("Romeo loves Juliet", "Romeo loves a girl")
en.corpus <- VCorpus(VectorSource(en))
tdm <- TermDocumentMatrix(en.corpus, 
                          control=list(wordLengths=c(1,Inf), 
                                       tokenize=function(x) ngram_tokenize(x, char=TRUE, 
                                                                           ngmin=3, ngmax=3)))
inspect(tdm)

ch <- c("abab", "aabb")
ch.corpus <- VCorpus(VectorSource(ch))
tdm <- TermDocumentMatrix(ch.corpus, 
                          control=list(wordLengths=c(1,Inf), 
                                       tokenize=function(x) ngram_tokenize(x, char=TRUE, 
                                                                           ngmin=1, ngmax=2)))
inspect(tdm)

Number of words in dictionary

Description

Counts total number of entries in dictionary.

Usage

numEntries(d)

Arguments

d

Dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

See Also

numPositiveEntries and numNegativeEntries for more option to count the number of entries

Examples

numEntries(SentimentDictionary(c("uncertain", "possible", "likely"))) # returns 3
numEntries(SentimentDictionary(c("increase", "rise", "more"),
                            c("fall", "drop"))) # returns 5
numEntries(SentimentDictionary(c("increase", "decrease", "exit"),
                               c(+1, -1, -10),
                               rep(NA, 3))) # returns 3

Number of negative words in dictionary

Description

Counts total number of negative entries in dictionary.

Usage

numNegativeEntries(d)

Arguments

d

is a dictionary of type SentimentDictionaryBinary or SentimentDictionaryWeighted

Note

Entries in SentimentDictionaryWeighted with a weight of 0 are not counted here

See Also

numEntries and numPositiveEntries for more option to count the number of entries

Examples

numNegativeEntries(SentimentDictionary(c("increase", "rise", "more"),
                            c("fall", "drop"))) # returns 2
numNegativeEntries(SentimentDictionary(c("increase", "decrease", "exit"),
                               c(+1, -1, -10),
                               rep(NA, 3))) # returns 2

Number of positive words in dictionary

Description

Counts total number of positive entries in dictionary.

Usage

numPositiveEntries(d)

Arguments

d

is a dictionary of type SentimentDictionaryBinary or SentimentDictionaryWeighted

Note

Entries in SentimentDictionaryWeighted with a weight of 0 are not counted here

See Also

numEntries and numNegativeEntries for more option to count the number of entries

Examples

numPositiveEntries(SentimentDictionary(c("increase", "rise", "more"),
                            c("fall", "drop"))) # returns 3
numPositiveEntries(SentimentDictionary(c("increase", "decrease", "exit"),
                               c(+1, -1, -10),
                               rep(NA, 3))) # returns 1

KDE plot of estimated coefficients

Description

Function performs a Kernel Density Estimation (KDE) of the coefficients and then plot these using ggplot. This type of plot allows to inspect whether the distribution of coefficients is skew. This can reveal if there are more positive terms than negative or vice versa.

Usage

## S3 method for class 'SentimentDictionaryWeighted'
plot(x, color = "gray60", theme = ggplot2::theme_bw(), ...)

Arguments

x

Dictionary of class SentimentDictionaryWeighted

color

Color for filling the density plot (default: gray color)

theme

Visualization theme for ggplot (default: is a black-white theme)

...

Additional parameters passed to function.

Value

Returns a plot of class ggplot

See Also

plotSentiment and plotSentimentResponse for further plotting options

Examples

d <- SentimentDictionaryWeighted(paste0(character(100), 1:100), rnorm(100), numeric(100))
plot(d)

# Change color in plot
plot(d, color="red")

library(ggplot2)
# Extend plot with additional layout options
plot(d) + ggtitle("KDE plot")
plot(d) + theme_void()

Line plot with sentiment scores

Description

Simple line plot to visualize the evolvement of sentiment scores. This is especially helpful when studying a time series of sentiment scores.

Usage

plotSentiment(
  sentiment,
  x = NULL,
  cumsum = FALSE,
  xlab = "",
  ylab = "Sentiment"
)

Arguments

sentiment

data.frame or numeric vector with sentiment scores

x

Optional parameter with labels or time stamps on x-axis.

cumsum

Parameter deciding whether the cumulative sentiment is plotted (default: cumsum=FALSE).

xlab

Name of x-axis (default: empty string).

ylab

Name of y-axis (default: "Sentiment").

Value

Returns a plot of class ggplot

See Also

plotSentimentResponse and plot.SentimentDictionaryWeighted for further plotting options

Examples

sentiment <- data.frame(Dictionary=runif(20))

plotSentiment(sentiment)
plotSentiment(sentiment, cumsum=TRUE)

# Change name of x-axis
plotSentiment(sentiment, xlab="Tone")

library(ggplot2)
# Extend plot with additional layout options
plotSentiment(sentiment) + ggtitle("Evolving sentiment")
plotSentiment(sentiment) + theme_void()

Scatterplot with trend line between sentiment and response

Description

Generates a scatterplot where points pairs of sentiment and the response variable. In addition, the plot addas a trend line in the form of a generalized additive model (GAM). Other smoothing variables are possible based on geom_smooth. This functions is helpful for visualization the relationship between computed sentiment scores and the gold standard.

Usage

plotSentimentResponse(
  sentiment,
  response,
  smoothing = "gam",
  xlab = "Sentiment",
  ylab = "Response"
)

Arguments

sentiment

data.frame with sentiment scores

response

Vector with response variables of the same length

smoothing

Smoothing functionality. Default is smoothing="gam" to utilize a generalized additive model (GAM). Other options can be e.g. a linear trend line (smoothing="lm"); see geom_smooth for a full list of options.

xlab

Description on x-axis (default: "Sentiment").

ylab

Description on y-axis (default: "Sentiment").

Value

Returns a plot of class ggplot

See Also

plotSentiment and plot.SentimentDictionaryWeighted for further plotting options

Examples

sentiment <- data.frame(Dictionary=runif(10))
response <- sentiment[[1]] + rnorm(10)

plotSentimentResponse(sentiment, response)

# Change x-axis
plotSentimentResponse(sentiment, response, xlab="Tone")

library(ggplot2)
# Extend plot with additional layout options
plotSentimentResponse(sentiment, response) + ggtitle("Scatterplot")
plotSentimentResponse(sentiment, response) + theme_void()

Prediction for given dictionary

Description

Function takes a dictionary of class SentimentDictionaryWeighted with weights as input. It then applies this dictionary to textual contents in order to calculate a sentiment score.

Usage

## S3 method for class 'SentimentDictionaryWeighted'
predict(
  object,
  newdata = NULL,
  language = "english",
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE),
  ...
)

Arguments

object

Dictionary of class SentimentDictionaryWeighted.

newdata

A vector of characters, a data.frame, an object of type Corpus, TermDocumentMatrix or DocumentTermMatrix .

language

Language used for preprocessing operations (default: English).

weighting

Function used for weighting of words; default is a a link to the tf-idf scheme.

...

Additional parameters passed to function for e.g. preprocessing.

Value

data.frame with predicted sentiment scores.

See Also

SentimentDictionaryWeighted, generateDictionary and compareToResponse for default dictionary generations

Examples

#' # Create a vector of strings
documents <- c("This is a good thing!",
               "This is a very good thing!",
               "This is okay.",
               "This is a bad thing.",
               "This is a very bad thing.")
response <- c(1, 0.5, 0, -0.5, -1)

# Generate dictionary with LASSO regularization
dictionary <- generateDictionary(documents, response)

# Compute in-sample performance
sentiment <- predict(dictionary, documents)
compareToResponse(sentiment, response)

Default preprocessing of corpus

Description

Preprocess existing corpus of type Corpus according to default operations. This helper function groups all standard preprocessing steps such that the usage of the package is more convenient.

Usage

preprocessCorpus(
  corpus,
  language = "english",
  stemming = TRUE,
  verbose = FALSE,
  removeStopwords = TRUE
)

Arguments

corpus

Corpus object which should be processed

language

Default language used for preprocessing (i.e. stop word removal and stemming)

stemming

Perform stemming (default: TRUE)

verbose

Print preprocessing status information

removeStopwords

Flag indicating whether to remove stopwords or not (default: yes)

Value

Object of Corpus

Output content of sentiment dictionary

Description

Prints entries of sentiment dictionary to the screen

Usage

## S3 method for class 'SentimentDictionaryWordlist'
print(x, ...)

## S3 method for class 'SentimentDictionaryBinary'
print(x, ...)

## S3 method for class 'SentimentDictionaryWeighted'
print(x, ...)

Arguments

x

Sentiment dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

...

Additional parameters passed to specific sub-routines

See Also

summary for showing a brief summary

Examples

print(SentimentDictionary(c("uncertain", "possible", "likely")))
print(SentimentDictionary(c("increase", "rise", "more"),
                          c("fall", "drop")))
print(SentimentDictionary(c("increase", "decrease", "exit"),
                          c(+1, -1, -10),
                          rep(NA, 3)))

Read dictionary from text file

Description

This routine reads a sentiment dictionary from a text file. Such a text file can be created e.g. via write. The dictionary type is recognized according to the internal format of the file.

Usage

read(file)

Arguments

file

File name pointing to text file

Value

Dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

See Also

write for creating such a file

Examples

d.out <- SentimentDictionary(c("uncertain", "possible", "likely"))
write(d.out, "example.dict")
d.in <- read("example.dict")
print(d.in)

d.out <- SentimentDictionary(c("increase", "rise", "more"),
                             c("fall", "drop"))
write(d.out, "example.dict")
d.in <- read("example.dict")
print(d.in)

d.out <- SentimentDictionary(c("increase", "decrease", "exit"),
                             c(+1, -1, -10),
                             rep(NA, 3),
                             intercept=5)
write(d.out, "example.dict")
d.in <- read("example.dict")
print(d.in)

unlink("example.dict")

Ridge estimation

Description

Function estimates coefficients based on ridge regularization.

Usage

ridgeEstimation(
  x,
  response,
  control = list(s = "lambda.min", family = "gaussian", grouped = FALSE),
  ...
)

Arguments

x

An object of type DocumentTermMatrix.

response

Response variable including the given gold standard.

control

(optional) A list of parameters defining the model as follows:

  • "s"Value of the parameter lambda at which the ridge is evaluated. Default is s="lambda.1se" which takes the calculated minimum value for \lambda and then subtracts one standard error in order to avoid overfitting. This often results in a better performance than using the minimum value itself given by lambda="lambda.min".

  • "family"Distribution for response variable. Default is family="gaussian". For non-negative counts, use family="poisson". For binary variables family="binomial". See glmnet for further details.

  • "grouped" Determines whether grouped function is used (with default FALSE).

...

Additional parameters passed to function for glmnet.

Value

Result is a list with coefficients, coefficient names and the model intercept.

Sentiment based on linear model

Description

Sentiment score as denoted by a linear model.

Usage

ruleLinearModel(dtm, d)

Arguments

dtm

Document-term matrix

d

Dictionary of type SentimentDictionaryWeighted

Value

Continuous sentiment score

Ratio of negative words

Description

Ratio of words labeled as negative in that dictionary compared to the total number of words in the document. Here, it uses the entry negativeWords of the SentimentDictionaryBinary.

Usage

ruleNegativity(dtm, d)

Arguments

dtm

Document-term matrix

d

Dictionary of type SentimentDictionaryBinary

Value

Ratio of negative words compared to all

Ratio of positive words

Description

Ratio of words labeled as positive in that dictionary compared to the total number of words in the document. Here, it uses the entry positiveWords of the SentimentDictionaryBinary.

Usage

rulePositivity(dtm, d)

Arguments

dtm

Document-term matrix

d

Dictionary of type SentimentDictionaryBinary

Value

Ratio of positive words compared to all

Ratio of dictionary words

Description

Ratio of words in that dictionary compared to the total number of words in the document

Usage

ruleRatio(dtm, d)

Arguments

dtm

Document-term matrix

d

Dictionary of type SentimentDictionaryWordlist with words belonging to a single category

Value

Ratio of dictionary words compared to all

Sentiment score

Description

Sentiment score defined as the difference between positive and negative word counts divided by the total number of words.

Usage

ruleSentiment(dtm, d)

Arguments

dtm

Document-term matrix

d

Dictionary of type SentimentDictionaryBinary

Details

Given the number of positive words P and the number of negative words N. Further, let T denote the total number of words in that document. Then, the sentiment ratio is defined as

\frac{P-N}{T}

. Here, it uses the entries negativeWords and positiveWords of the SentimentDictionaryBinary.

Value

Sentiment score in the range of -1 to 1.

Sentiment polarity score

Description

Sentiment score defined as the difference between positive and negative word counts divided by the sum of positive and negative words.

Usage

ruleSentimentPolarity(dtm, d)

Arguments

dtm

Document-term matrix

d

Dictionary of type SentimentDictionaryBinary

Details

Given the number of positive words P and the number of negative words N. Then, the sentiment ratio is defined as

\frac{P-N}{P+N}

. Here, it uses the entries negativeWords and positiveWords of the SentimentDictionaryBinary.

Value

Sentiment score in the range of -1 to 1.

Counts word frequencies

Description

Counts total word frequencies in each document

Usage

ruleWordCount(dtm)

Arguments

dtm

Document-term matrix

Value

Total number of words

Spike-and-slab estimation

Description

Function estimates coefficients based on spike-and-slab regression.

Usage

spikeslabEstimation(
  x,
  response,
  control = list(n.iter1 = 500, n.iter2 = 500),
  ...
)

Arguments

x

An object of type DocumentTermMatrix.

response

Response variable including the given gold standard.

control

(optional) A list of parameters defining the LASSO model. Default isn.iter1=500 and n.iter2=500. See spikeslab for details.

...

Additional parameters passed to function for spikeslab.

Value

Result is a list with coefficients, coefficient names and the model intercept.

Output summary information on sentiment dictionary

Description

Output summary information on sentiment dictionary

Usage

## S3 method for class 'SentimentDictionaryWordlist'
summary(object, ...)

## S3 method for class 'SentimentDictionaryBinary'
summary(object, ...)

## S3 method for class 'SentimentDictionaryWeighted'
summary(object, ...)

Arguments

object

Sentiment dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

...

Additional parameters passed to specific sub-routines

See Also

print for output the entries of a dictionary

Examples

summary(SentimentDictionary(c("uncertain", "possible", "likely")))
summary(SentimentDictionary(c("increase", "rise", "more"),
                            c("fall", "drop")))
summary(SentimentDictionary(c("increase", "decrease", "exit"),
                            c(+1, -1, -10),
                            rep(NA, 3)))

Default preprocessing of corpus and conversion to document-term matrix

Description

Preprocess existing corpus of type Corpus according to default operations. This helper function groups all standard preprocessing steps such that the usage of the package is more convenient. The result is a document-term matrix.

Usage

toDocumentTermMatrix(
  x,
  language = "english",
  minWordLength = 3,
  sparsity = NULL,
  removeStopwords = TRUE,
  stemming = TRUE,
  weighting = function(x) tm::weightTfIdf(x, normalize = FALSE)
)

Arguments

x

Corpus object which should be processed

language

Default language used for preprocessing (i.e. stop word removal and stemming)

minWordLength

Minimum length of words used for cut-off; i.e. shorter words are removed. Default is 3.

sparsity

A numeric for the maximal allowed sparsity in the range from bigger zero to smaller one. Default is NULL in order suppress this functionality.

removeStopwords

Flag indicating whether to remove stopwords or not (default: yes)

stemming

Perform stemming (default: TRUE)

weighting

Function used for weighting of words; default is a a link to the tf-idf scheme.

Value

Object of DocumentTermMatrix

See Also

DocumentTermMatrix for the underlying class

Transforms the input into a Corpus object

Description

Takes the given input of characters and transforms it into a Corpus. The input is checked to match the expected class and format.

Usage

transformIntoCorpus(x)

Arguments

x

A list, data.frame or vector consisting of characters

Value

The generated Corpus

Note

Factors are automatically casted into characters but with printing a warning

See Also

preprocessCorpus for further preprocessing, analyzeSentiment for subsequent sentiment analysis

Examples

transformIntoCorpus(c("Document 1", "Document 2", "Document 3"))
transformIntoCorpus(list("Document 1", "Document 2", "Document 3"))
transformIntoCorpus(data.frame("Document 1", "Document 2", "Document 3"))

Write dictionary to text file

Description

This routine exports a sentiment dictionary to a text file which can be the source for additional problems or controlling the output.

Usage

write(d, file)

## S3 method for class 'SentimentDictionaryWordlist'
write(d, file)

## S3 method for class 'SentimentDictionaryBinary'
write(d, file)

## S3 method for class 'SentimentDictionaryWeighted'
write(d, file)

Arguments

d

Dictionary of type SentimentDictionaryWordlist, SentimentDictionaryBinary or SentimentDictionaryWeighted

file

File to which the dictionary should be exported

See Also

read for later access

Examples

d.out <- SentimentDictionary(c("uncertain", "possible", "likely"))
write(d.out, "example.dict")
d.in <- read("example.dict")
print(d.in)

d.out <- SentimentDictionary(c("increase", "rise", "more"),
                             c("fall", "drop"))
write(d.out, "example.dict")
d.in <- read("example.dict")
print(d.in)

d.out <- SentimentDictionary(c("increase", "decrease", "exit"),
                             c(+1, -1, -10),
                             rep(NA, 3),
                             intercept=5)
write(d.out, "example.dict")
d.in <- read("example.dict")
print(d.in)

unlink("example.dict")