跨多个变量循环 grep

Question

我正在尝试使用 grep 来识别哪些观察结果与某个正则表达式匹配。但棘手的是，潜在的匹配分布在多个列中。

复制样本数据：

df <- matrix(nrow = 12, ncol = 20) %>% as.data.frame()
names(df) <- paste0("col", 1:20)
for (i in 1:20){
  df[,i] <- month.name[sample(1:12, 12, replace = T)]
}
df$July.dummy <- 0

我一直在尝试在潜在变量上循环

grep

表达式来识别匹配项。在样本数据中，目标是识别“July”出现在 col1 到 col20 中任何一个中的所有观测值，并相应地将

df$July.dummy

更改为 1。

all.cols <- paste0("col", 1:20)
for (VAR in all.cols){
  df$July.dummy[grep("July", noquote(paste0("df$", VAR)))] <- 1
}

此代码片段成功执行，每个组件似乎都“工作”......但没有任何观察结果发生改变。

我很高兴考虑其他非循环/非 grep 解决方案，但如果有人可以向我展示为什么我尝试的解决方案不起作用，以供我自己启发，我也会很感激。谢谢！

Answer 1

假设您使用

grep

因为您实际上需要正则表达式匹配，一种可能是：

df$July.dummy <- apply(df[-length(df)], 1, \(x) as.numeric(any(grep("July", x))))

但是，如果您不需要使用正则表达式而只想进行相等比较，您可以这样做：

df$July.dummy <- as.numeric(rowSums(df[-length(df)] == "July") > 0)

Answer 2

library(tidyverse)

df |> 
  filter(if_any(any_of(all.cols), \(x) str_detect(x, "July")))
#>        col1      col2     col3     col4     col5     col6      col7     col8
#> 1   October       May      May    March    March December      July    March
#> 2   October  November  October    March     July December       May      May
#> 3       May September December   August  October     June   January    April
#> 4     March    August February  January  October February       May    March
#> 5   January  December     July  October    March   August      June  October
#> 6     April     March December February     June February  December December
#> 7  February      July  October     July     June   August September     July
#> 8     March  February  January     June November  January      July February
#> 9     April   October November  January February      May      July December
#> 10 December  February  October November   August    April September  October
#> 11  January     March  January   August     June February     March     July
#>        col9     col10     col11     col12    col13    col14    col15     col16
#> 1     April     March   January       May  January     June November   January
#> 2  November  November  December  December    March     July    April   October
#> 3      June   October     March  February     July  January      May  November
#> 4      June  December       May    August     June     July     June     April
#> 5      July     April  December       May November     July February    August
#> 6   January     March     April  December     July     July      May  November
#> 7   January  February September      July      May     July  October      July
#> 8     March     March      July  December   August November December  December
#> 9      July      June      July September      May   August      May  November
#> 10    March  November      July     April February December February September
#> 11     July September  November  November    March  January    April  February
#>        col17     col18     col19     col20 July.dummy
#> 1    January    August     March  February          0
#> 2   November       May  November   October          0
#> 3   December       May      June  February          0
#> 4      April     March      June     March          0
#> 5    January  February   October      July          0
#> 6       July      July       May     April          0
#> 7  September      July  November September          0
#> 8      April  November   October       May          0
#> 9   December     April  February      July          0
#> 10     March September September   October          0
#> 11       May  February  February   October          0