1d:T765,# Compare term usage across 2 document groups using the Chi-square Test for Count Data Perform a `chisq.test` to compare if groups of documents have more prevalence of specific terms. The function looks to each term in the document term matrix and applies a `chisq.test` comparing the frequency of occurrence of each term compared to the other terms in the document group. ```r dtm_chisq(dtm, groups, correct = TRUE, ...) ``` ## Arguments - `dtm`: a document term matrix: an object returned by `document_term_matrix` - `groups`: a logical vector with 2 groups (TRUE / FALSE) where the size of the `groups` vector is the same as the number of rows of `dtm` and where element i corresponds row i of `dtm` - `correct`: passed on to `chisq.test` - `...`: further arguments passed on to `chisq.test` ## Returns a data.frame with columns term, chisq, p.value, freq, freq_true, freq_false indicating for each term in the `dtm`, how frequently it occurs in each group, the Chi-Square value and it's corresponding p-value. ## Examples ```r data(brussels_reviews_anno) ## ## Which nouns occur in text containing the term 'centre' ## x <- subset(brussels_reviews_anno, xpos == "NN" & language == "fr") x <- x[, c("doc_id", "lemma")] x <- document_term_frequencies(x) dtm <- document_term_matrix(x) relevant <- dtm_chisq(dtm, groups = dtm[, "centre"] > 0) head(relevant, 10) ## ## Which adjectives occur in text containing the term 'hote' ## x <- subset(brussels_reviews_anno, xpos == "JJ" & language == "fr") x <- x[, c("doc_id", "lemma")] x <- document_term_frequencies(x) dtm <- document_term_matrix(x) group <- subset(brussels_reviews_anno, lemma %in% "hote") group <- rownames(dtm) %in% group$doc_id relevant <- dtm_chisq(dtm, groups = group) head(relevant, 10) ## Not run: # do not show scientific notation of the p-values options(scipen = 100) head(relevant, 10) ## End(Not run) ```1e:T49a,M7.49933 0.25C3.49635 0.25 0.25 3.49593 0.25 7.50024C0.25 10.703 2.32715 13.4206 5.2081 14.3797C5.57084 14.446 5.70302 14.2222 5.70302 14.0

dtm_chisq function