udpipe (version 0.8.11)

dtm_remove_tfidf: Remove terms from a Document-Term-Matrix and documents with no terms based on the term frequency inverse document frequency

Description

Remove terms from a Document-Term-Matrix and documents with no terms based on the term frequency inverse document frequency. Either giving in the maximum number of terms (argument top), the tfidf cutoff (argument cutoff) or a quantile (argument prob)

Usage

dtm_remove_tfidf(dtm, top, cutoff, prob, remove_emptydocs = TRUE)

Value

a sparse Matrix as returned by sparseMatrix

where terms with high tfidf are kept and documents without any remaining terms are removed

Arguments

dtm

an object returned by document_term_matrix

top

integer with the number of terms which should be kept as defined by the highest mean tfidf

cutoff

numeric cutoff value to keep only terms in dtm where the tfidf obtained by dtm_tfidf is higher than this value

prob

numeric quantile indicating to keep only terms in dtm where the tfidf obtained by dtm_tfidf is higher than the prob percent quantile

remove_emptydocs

logical indicating to remove documents containing no more terms after the term removal is executed. Defaults to TRUE.

Examples

data(brussels_reviews_anno)
x <- subset(brussels_reviews_anno, xpos == "NN")
x <- x[, c("doc_id", "lemma")]
x <- document_term_frequencies(x)
dtm <- document_term_matrix(x)
dtm <- dtm_remove_lowfreq(dtm, minfreq = 10)
dim(dtm)

## Keep only terms with high tfidf
x <- dtm_remove_tfidf(dtm, top=50)
dim(x)
x <- dtm_remove_tfidf(dtm, top=50, remove_emptydocs = FALSE)
dim(x)

## Keep only terms with tfidf above 1.1
x <- dtm_remove_tfidf(dtm, cutoff=1.1)
dim(x)

## Keep only terms with tfidf above the 60 percent quantile
x <- dtm_remove_tfidf(dtm, prob=0.6)
dim(x)