textstat_frequency: Tabulate feature frequencies

Description Usage Arguments Value Examples

Description

Produces counts and document frequencies summaries of the features in a dfm, optionally grouped by a docvars variable or other supplied grouping variable.

Usage

1
2
textstat_frequency(x, n = NULL, groups = NULL, ties_method = c("min",
  "average", "first", "random", "max", "dense"), ...)

Arguments

x

a dfm object

n

(optional) integer specifying the top n features to be returned, within group if groups is specified

groups

either: a character vector containing the names of document variables to be used for grouping; or a factor or object that can be coerced into a factor equal in length or rows to the number of documents. See groups for details.

ties_method

character string specifying how ties are treated. See frank for details. Unlike that function, however, the default is "min", so that frequencies of 10, 10, 11 would be ranked 1, 1, 3.

...

additional arguments passed to dfm_group. This can be useful in passing 'force = TRUE', for instance, if you are grouping a dfm that has been weighted.

Value

a data.frame containing the following variables:

feature

(character) the feature

frequency

count of the feature

rank

rank of the feature, where 1 indicates the greatest frequency

docfreq

document frequency of the feature, as a count (the number of documents in which this feature occurred at least once)

docfreq

document frequency of the feature, as a count

group

(only if groups is specified) the label of the group. If the features have been grouped, then all counts, ranks, and document frequencies are within group. If groups is not specified, the group column is omitted from the returned data.frame.

textstat_frequency returns a data.frame of features and their term and document frequencies within groups.

Examples

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
set.seed(20)
dfmat1 <- dfm(c("a a b b c d", "a d d d", "a a a"))
textstat_frequency(dfmat1)
textstat_frequency(dfmat1, groups = c("one", "two", "one"), ties_method = "first")
textstat_frequency(dfmat1, groups = c("one", "two", "one"), ties_method = "dense")

dfmat2 <- corpus_subset(data_corpus_inaugural, President == "Obama") %>%
   dfm(remove_punct = TRUE, remove = stopwords("english"))
tstat1 <- textstat_frequency(dfmat2)
head(tstat1, 10)


# plot 20 most frequent words
library("ggplot2")
ggplot(tstat1[1:20, ], aes(x = reorder(feature, frequency), y = frequency)) +
    geom_point() + 
    coord_flip() +
    labs(x = NULL, y = "Frequency")

# plot relative frequencies by group
dfmat3 <- data_corpus_inaugural %>% 
    corpus_subset(Year > 2000) %>% 
    dfm(remove = stopwords("english"), remove_punct = TRUE) %>% 
    dfm_group(groups = "President") %>%
    dfm_weight(scheme = "prop")

# calculate relative frequency by president
tstat2 <- textstat_frequency(dfmat3, n = 10, groups = "President")

# plot frequencies
ggplot(data = tstat2, aes(x = factor(nrow(tstat2):1), y = frequency)) +
    geom_point() +
    facet_wrap(~ group, scales = "free") +
    coord_flip() +
    scale_x_discrete(breaks = nrow(tstat2):1,
                       labels = tstat2$feature) +
    labs(x = NULL, y = "Relative frequency")

quanteda/quanteda documentation built on June 26, 2019, 3:38 a.m.