如何创建与 quanteda 的交互？

Question

考虑以下示例

library(quanteda)
library(tidyverse)

tibble(text = c('the dog is growing tall',
                'the grass is growing as well')) %>% 
  corpus() %>% dfm()
Document-feature matrix of: 2 documents, 8 features (31.2% sparse).
       features
docs    the dog is growing tall grass as well
  text1   1   1  1       1    1     0  0    0
  text2   1   0  1       1    0     1  1    1

我想在每个句子中创建dog 和其他标记之间的交互。也就是说，创建功能the-dog、is-dog、growing-dog、tall-dog 并将它们添加到dfm（在我们已经拥有的之上）。

也就是说，例如，如果the 和dog 都出现在句子中，the-dog 将等于 1（否则为零）。所以the-dog 第一句是一个，第二句是零。

请注意，我只在句子中出现dog 时才创建交互术语，因此此处不需要dog-grass。

如何在quanteda 中有效地做到这一点？

Answer 1

library("quanteda")
## Package version: 2.1.2

toks <- tokens(c(
  "the dog is growing tall",
  "the grass is growing as well"
))

# now keep just tokens co-occurring with "dog"
toks_dog <- tokens_select(toks, "dog", window = 1e5)

# create the dfm and label other terms as interactions with dog
dfmat_dog <- dfm(toks_dog) %>%
  dfm_remove("dog")
colnames(dfmat_dog) <- paste(featnames(dfmat_dog), "dog", sep = "-")
dfmat_dog
## Document-feature matrix of: 2 documents, 4 features (50.00% sparse) and 0 docvars.
##        features
## docs    the-dog is-dog growing-dog tall-dog
##   text1       1      1           1        1
##   text2       0      0           0        0

# combine with other features
print(cbind(dfm(toks), dfmat_dog), max_nfeat = -1)
## Document-feature matrix of: 2 documents, 12 features (37.50% sparse) and 0 docvars.
##        features
## docs    the dog is growing tall grass as well the-dog is-dog growing-dog
##   text1   1   1  1       1    1     0  0    0       1      1           1
##   text2   1   0  1       1    0     1  1    1       0      0           0
##        features
## docs    tall-dog
##   text1        1
##   text2        0

^{由reprex package (v1.0.0) 于 2021-03-18 创建}