在几列中拆分一列字符串

我有数据框

df=data.frame(x=rnorm(8),y=runif(8),longstring=c("foo_100_Case1","foo_125_Case1","bar_100_Case1","bar_125_Case1","foo_100_Case2","foo_125_Case2","bar_100_Case2","bar_125_Case2"),stringsAsFactors = F)

我需要将最后一列拆分为三列,分隔符为"_".我一直在做以下事情:

a=matrix(unlist(strsplit(df$longstring,"_",fixed=T)),8,3,byrow = T)
df$type=a[,1]
df$point=a[,2]
df$case=a[,3]

但我想知道是否有一种更简单的方法:组合strsplit和unlist特别笨拙,并且它不会使代码非常易读.

以下是一些可供尝试的选项:

我的"splitstackshape"包是专为这种东西设计的......

library(splitstackshape)
cSplit(df, "longstring", "_")
#              x         y longstring_1 longstring_2 longstring_3
# 1: -1.41524742 0.2123978          foo          100        Case1
# 2: -1.09240237 0.3899935          foo          125        Case1
# 3:  0.39675025 0.2162463          bar          100        Case1
# 4: -1.14996728 0.7608128          bar          125        Case1
# 5: -0.07657172 0.6878348          foo          100        Case2
# 6:  0.29549599 0.2216566          foo          125        Case2
# 7:  1.78622612 0.1496666          bar          100        Case2
# 8: -0.11749579 0.9255409          bar          125        Case2

"data.table"包给我们带来了快速的tstrsplit功能......

library(data.table)
as.data.table(df)[
  , paste0("V", 1:3) := tstrsplit(longstring, "_")][
    , longstring := NULL][]

如果你有时间并且想等待read.table它的工作......

cbind(df[1:2], read.table(text = df$longstring, sep = "_"))

如果你需要其他快速的东西......

library(iotools)
cbind(df[1:2], mstrsplit(df$longstring, sep = "_"))