整洁的文本格式内的单词替换

Question

嗨,我正在使用tidy_text格式,我试图将字符串"电子邮件"和"电子邮件"替换为"电子邮件".

set.seed(123)
terms <- c("emails are nice", "emailing is fun", "computer freaks", "broken modem")
df <- data.frame(sentence = sample(terms, 100, replace = TRUE))
df
str(df)
df$sentence <- as.character(df$sentence)
tidy_df <- df %>% 
unnest_tokens(word, sentence)

tidy_df %>% 
count(word, sort = TRUE) %>% 
filter( n > 20) %>% 
mutate(word = reorder(word, n)) %>% 
ggplot(aes(word, n)) +
geom_col() +
xlab(NULL) + 
coord_flip()

这工作正常,但当我使用:

 tidy_df <- gsub("emailing", "email", tidy_df)

替换单词并再次运行条形图我收到以下错误消息:

UseMethod("group_by_")中的错误:没有适用于"group_by_"的方法应用于类"character"的对象

有没有人知道如何在不改变tidy_text的结构/类的情况下,在整洁的文本格式中轻松替换单词？

Answer 1

删除像这样的单词的结尾称为词干,如果你愿意,R中有几个包可以为你做这些.一个是来自rOpenSci的hunspell包,另一个选项是实现Porter算法干扰的SnowballC包.你会这样实现:

library(dplyr)
library(tidytext)
library(SnowballC)

terms <- c("emails are nice", "emailing is fun", "computer freaks", "broken modem")

set.seed(123)
data_frame(txt = sample(terms, 100, replace = TRUE)) %>%
        unnest_tokens(word, txt) %>%
        mutate(word = wordStem(word))
#> # A tibble: 253 × 1
#>      word
#>     <chr>
#> 1   email
#> 2       i
#> 3     fun
#> 4  broken
#> 5   modem
#> 6   email
#> 7       i
#> 8     fun
#> 9  broken
#> 10  modem
#> # ... with 243 more rows

请注意,它会阻止您的所有文本,并且某些单词不再像真正的单词; 你可能会或可能不会关心这一点.

如果你不希望使用干像SnowballC或一个的hunspell词干的所有文字,你可以使用dplyr是if_else内mutate()只更换特定的单词.

set.seed(123)
data_frame(txt = sample(terms, 100, replace = TRUE)) %>%
        unnest_tokens(word, txt) %>%
        mutate(word = if_else(word %in% c("emailing", "emails"), "email", word))
#> # A tibble: 253 × 1
#>      word
#>     <chr>
#> 1   email
#> 2      is
#> 3     fun
#> 4  broken
#> 5   modem
#> 6   email
#> 7      is
#> 8     fun
#> 9  broken
#> 10  modem
#> # ... with 243 more rows

或者str_replace从stringr包中使用它可能更有意义.

library(stringr)
set.seed(123)
data_frame(txt = sample(terms, 100, replace = TRUE)) %>%
        unnest_tokens(word, txt) %>%
        mutate(word = str_replace(word, "email(s|ing)", "email"))
#> # A tibble: 253 × 1
#>      word
#>     <chr>
#> 1   email
#> 2      is
#> 3     fun
#> 4  broken
#> 5   modem
#> 6   email
#> 7      is
#> 8     fun
#> 9  broken
#> 10  modem
#> # ... with 243 more rows