在 data.table v.1.9.6您可以像这样在列中拆分变量:
library(data.table)
DT = data.table(x=c("A/B", "A", "B"), y=1:3)
DT[, c("c1", "c2") := tstrsplit(x, "/", fixed=TRUE)][]
所需的拆分数量 [above: 2] 并不总是事先知道。
当拆分数量已知时，如何生成所需的变量名称？
n = 2 # desired number of splits
# naive attempt to build required string
m = paste0("'", "myvar", 1:n, "'", collapse = ",")
m = paste0("c(", m, ")" )
# [1] "c('myvar1','myvar2','myvar3')"
DT[, m := tstrsplit(x, "/", fixed=TRUE)][] # doesn't work
最佳答案
两种方法。第一个强烈建议:
#one
n=2
DT[, paste0("myvar", 1:n) := tstrsplit(x, "/", fixed=T)][]
# x y myvar1 myvar2
#1: A/B 1 A B
#2: A 2 A NA
#3: B 3 B NA
#two
DT[, eval(parse(text=m)) := tstrsplit(x, "/", fixed=TRUE)][]
# x y myvar1 myvar2
#1: A/B 1 A B
#2: A 2 A NA
#3: B 3 B NA
额外
如果您事先不知道拆分的数量:
splits <- max(lengths(strsplit(DT$x, "/")))
DT[, paste0("myvar", 1:splits) := tstrsplit(x, "/", fixed=T)][]
关于r - 在 data.table tstrsplit 中动态分配分割数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33200179/