Question

我正在尝试使用left_join运算符创建一个复制此函数的函数：

df1 <- data.frame(
  name = c("John", "Paul", "George", "Ringo", "Stuart", "Pete"),
  instrument = c("guitar", "bass", "guitar", "drums", "bass",
                 "drums"),stringsAsFactors=FALSE)
df2 <- data.frame(
  name2 = c("John", "Paul", "George", "Ringo", "Brian"),
  band = c("TRUE", "TRUE", "TRUE", "TRUE", "FALSE"),stringsAsFactors=FALSE) 

z <- left_join(df1, df2, by = c("name" = "name2"))

这按预期工作，但是如果我创建这样的函数：

left <- function(x,y,id1) {
  left_join(x, y, by = c(id1 = "name2"))
}

left(df1,df2,name)

现在我得到一个错误：

Error: `by` can't contain join column `id1` which is missing from LHS

我一直在和bang bang，quo运算符和!!但是我无法通过传递id1作为参数来使其工作。

注意：这是简化管道（％>％）过程的过程，但主要问题是无法在c（）函数内调用id1。

Answer 1

您可以使用setNames

left <- function(x, y, id1) {
    left_join(x, y, by = setNames("name2", id1))
}

left(df1, df2, "name")
#    name instrument band
#1   John     guitar TRUE
#2   Paul       bass TRUE
#3 George     guitar TRUE
#4  Ringo      drums TRUE
#5 Stuart       bass <NA>
#6   Pete      drums <NA>

R dyplr left_join在函数内部不起作用

1 个答案: