R – 如何从多个匹配中替换字符串(在数据框中)

2019年7月2日 288次阅读

我需要用一些存储在数据帧中的匹配替换字符串的子集.

例如 –

input_string = "Whats your name and Where're you from"

我需要从数据框中替换此字符串的一部分.说数据框是

matching <- data.frame(from_word=c("Whats your name", "name", "fro"),
            to_word=c("what is your name","names","froth"))

输出预期是你的名字和你来自哪里

注意 –

>它匹配最大字符串.在此示例中,name与名称不匹配,因为name是较大匹配的一部分
>它必须匹配整个字符串而不是部分字符串.来自“来自”不应该匹配为“泡沫”

我提到了下面的链接,但不知何故无法按照预期/如上所述进行此工作

Match and replace multiple strings in a vector of text without looping in R

这是我在此的头一篇博文.如果我没有提供足够的细节,请告诉我

最佳答案 编辑

根据斯里兰卡评论的意见,我建议使用：

library(gsubfn)
# words to be replaced
a <-c("Whats your","Whats your name", "name", "fro")
# their replacements
b <- c("What is yours","what is your name","names","froth")
# named list as an input for gsubfn
replacements <- setNames(as.list(b), a)
# the test string
input_string = "fro Whats your name and Where're name you from to and fro I Whats your"
# match entire words
gsubfn(paste(paste0("\\w*", names(replacements), "\\w*"), collapse = "|"), replacements, input_string)

原版的

我不会说这比你的简单循环更容易阅读,但它可能需要更好地照顾重叠的替换：

# define the sample dataset
input_string = "Whats your name and Where're you from"
matching <- data.frame(from_word=c("Whats your name", "name", "fro", "Where're", "Whats"),
                       to_word=c("what is your name","names","froth", "where are", "Whatsup"))

# load used library
library(gsubfn)

# make sure data is of class character
matching$from_word <- as.character(matching$from_word)
matching$to_word <- as.character(matching$to_word)

# extract the words in the sentence
test <- unlist(str_split(input_string, " "))
# find where individual words from sentence match with the list of replaceble words
test2 <- sapply(paste0("\\b", test, "\\b"), grepl, matching$from_word)
# change rownames to see what is the format of output from the above sapply
rownames(test2) <- matching$from_word
# reorder the data so that largest replacement blocks are at the top
test3 <- test2[order(rowSums(test2), decreasing = TRUE),]
# where the word is already being replaced by larger chunk, do not replace again
test3[apply(test3, 2, cumsum) > 1] <- FALSE

# define the actual pairs of replacement
replacements <- setNames(as.list(as.character(matching[,2])[order(rowSums(test2), decreasing = TRUE)][rowSums(test3) >= 1]),
                         as.character(matching[,1])[order(rowSums(test2), decreasing = TRUE)][rowSums(test3) >= 1])

# perform the replacement
gsubfn(paste(as.character(matching[,1])[order(rowSums(test2), decreasing = TRUE)][rowSums(test3) >= 1], collapse = "|"),
       replacements,input_string)
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