我怎样才能收集所有专栏，而不是一个专栏？

Question

我需要gather_在数据帧的所有列上，除了一个。例如：

# I want to generate a dataframe whose column names are the letters of the alphabet. If you know of a simpler way, let me know! 
foo <- as.data.frame(matrix(runif(100), 10, 10)) 
colnames(foo) <- letters[1:10] 

现在，假设我要收集所有列，除了e列。这是行不通的：

mycol <- "e" 
foo_melt <- gather_(foo, key = "variable", value = "value", -mycol) 
#Error in -mycol : invalid argument to unary operator 

这将：如果你问我

column_list <- colnames(foo) 
column_list <- column_list[column_list != mycol] 
foo_melt <- gather_(foo, key = "variable", value = "value", column_list) 

看起来颇为费解。没有更简单的方法吗？

Answer 1

一种选择是one_of与gather

res1 <- gather(foo, key = "variable", value = "value", -one_of(mycol)) 

，如果我们需要gather_，然后setdiff可用于

res2 <- gather_(foo, key = "variable", value = "value", setdiff(names(foo), mycol)) 

identical(res1, res2) 
#[1] TRUE 
dim(res1) 
#[1] 90 3 

head(res1, 3) 
#   e variable  value 
#1 0.8484310  a 0.2730847 
#2 0.0501665  a 0.8129584 
#3 0.6689233  a 0.5457884 

Answer 2

试试这个：

foo_melt <- gather_(foo, key = "variable", value = "value",names(foo)[-5]) 

这会给你一切除第5个（“e”）以外的列。

> head(foo_melt) 
      e variable  value 
1 0.6359394  a 0.9567835 
2 0.1558724  a 0.7778139 
3 0.1418696  a 0.2132809 
4 0.7184244  a 0.4539194 
5 0.4487064  a 0.1049392 
6 0.5963304  a 0.8692680