将数据框中的字符向量与另一个字符向量匹配并修剪字符 [英] Match character vector in a dataframe with another character vector and trim character

问题描述

这是一个数据框和一个向量.

Here is a dataframe and a vector.

df1  <-  tibble(var1 = c("abcd", "efgh", "ijkl", "qrst"))

vec <-  c("abcd", "mnop", "ijkl")

现在，对于var1中与vec中的值匹配的所有值，在var1中仅保留前3个字符，以便所需的解决方案是:

Now, for all the values in var1 that matches with the values in vec, keep only first 3 characters in var1 such that the desired solution is:

df2 <- tibble(var1 = c("abc", "efgh", "ijk", "qrst"))

由于"abcd"匹配，因此在df2中仅保留3个字符，即"abc"，但在vec中不存在"efgh"，因此在df2中将其保留为即"efgh".

Since, "abcd" matches, we keep only 3 characters i.e. "abc" in df2, but "efgh" doesn't exist in vec, so we keep it as is i.e "efgh" in df2.

如何使用dplyr和/或stringr完成此操作?

How can I use dplyr and/or stringr to accomplish this?

推荐答案

您可以只使用％in％来检查字符串是否在向量中，并使用 substr 修剪矢量:

You can just use %in% to check whether the strings are in the vector, and substr to trim the vector:

df1 %>% 
    mutate(var1 = ifelse(var1 %in% vec, substr(var1, 1, 3), var1))

# A tibble: 4 x 1
#  var1 
#  <chr>
#1 abc  
#2 efgh 
#3 ijk  
#4 qrst

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