Question

我有以下包含字符和数字以及NA的数据框：

df <- data.frame(a=c("notfound","NOT FOUND","NOT FOUND"), b=c(NA,"NOT FOUND","NOT FOUND"), c=c("not found",2,3), d=c("not   found","NOT FOUND","NOT FOUND"), e=c("234","NOT FOUND",NA))

          a         b         c           d         e
1  notfound      <NA> not found not   found       234
2 NOT FOUND NOT FOUND         2   NOT FOUND NOT FOUND
3 NOT FOUND NOT FOUND         3   NOT FOUND      <NA>

我想删除所有条目“未找到”，“未找到”，“未找到”，“未找到”的所有列。基本上是tolower(gsub(" ","",df)=="notfound")。似乎此操作不适用于数据帧。有其他选择吗？

所需的输出将是：

         d            e
1    not found          234
2            2    NOT FOUND
3            3         <NA>

Answer 1

您可以将grepl与正则表达式一起使用，以搜索与该表达式匹配的字符串，并仅保留某些元素未显示匹配项的列（由FALSE grepl表示）），以使该列的匹配数小于nrow(df)。此模式匹配以“ not”开头和以“ found”结尾的字符串，并且grepl设置为不区分大小写。

is_nf <- 
  sapply(df, grepl, pattern = '(?=^not).*found$', 
         perl = TRUE, ignore.case = TRUE)


df[colSums(is_nf) < nrow(df)]
#           b         c         e
# 1      <NA> not found       234
# 2 NOT FOUND         2 NOT FOUND
# 3 NOT FOUND         3      <NA>

我猜您也想删除唯一未找到“ NA”的列。

is_na <- is.na(df)

df[colSums(is_nf | is_na) < nrow(df)]
#           c         e
# 1 not found       234
# 2         2 NOT FOUND
# 3         3      <NA>

从数据框中删除具有重复值的列

1 个答案: