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r - 带有 %>% 的多个条件

问题描述

这似乎是一个应该在 stackoverflow/google 中的问题，但它不是（或者至少我找不到它）所以我会在这里问它：

可重现的例子：

colnames(df)
"Z1"   "Z2"   "Z3"   "GV1"  "GV2"  "GV3"  "GV4"  "GV5"  "GV6"  "GV7"  "GV8"  "GV9" "GVY"  "EN1" "EN2"  "EN3"  "EN4"  "EN5"  "EN6"  "EN7"  "EN8"  "EN9"  "ENY"  "PV1"  "PV2"  "PV3"  "PV4"  "PV5"  "PV6"  "PV7"  "PVY"

我正在尝试理解/执行下一个代码：

colnames(df[substr(colnames(df),start=1,stop=2) == "GV" & substr(colnames(df),start=3,stop=3) != "Y"])

使用 magrittr 管道运算符%>%，因为我喜欢将它用于更易读的代码（这有效）：

library(magrittr)
df %>%
  colnames %>%
    substr(start=1,stop=2) == "GV"

但是，这样做没有意义（这不起作用）：

df %>%
  colnames %>%
    substr(start=1,stop=2) == "GV" & substr(colnames(df),start=3,stop=3) != "Y"]

有任何想法吗？

标签： rconditionalmagrittr

解决方案

如果您的目标是简化代码，那么您可以使用正则表达式：

# Match string that starts with GV and is not fallowed by Y
grep("^GV[^Y]", foo, value = TRUE)
# [1] "GV1" "GV2" "GV3" "GV4" "GV5" "GV6" "GV7" "GV8" "GV9"

# Data
foo <- c("Z1", "Z2", "Z3", "GV1", "GV2", "GV3", "GV4", "GV5", "GV6", "GV7", "GV8", "GV9", "GVY", "EN1", "EN2", "EN3", "EN4", "EN5", "EN6", "EN7", "EN8", "EN9", "ENY", "PV1", "PV2", "PV3", "PV4", "PV5", "PV6", "PV7", "PVY")

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