我想计算data.table中每个列的平均值,按另一列分组.我的问题类似于关于SO的另外两个问题(一个和两个),但我不能将这些问题应用于我的问题.
这是一个例子:
library(data.table)
dtb <- fread(input = "condition,var1,var2,var3
one,100,1000,10000
one,101,1001,10001
one,102,1002,10002
two,103,1003,10003
two,104,1004,10004
two,105,1005,10005
three,106,1006,10006
three,107,1007,10007
three,108,1008,10008
four,109,1009,10009
four,110,1010,10010")
dtb
# condition var1 var2 var3
# 1: one 100 1000 10000
# 2: one 101 1001 10001
# 3: one 102 1002 10002
# 4: two 103 1003 10003
# 5: two 104 1004 10004
# 6: two 105 1005 10005
# 7: three 106 1006 10006
# 8: three 107 1007 10007
# 9: three …我想要添加一个列,data.table它是几个其他列的串联,其中的名称我存储在向量中cols.根据/sf/answers/1517778181/我试过do.call+ paste但无法使其正常工作.这是我尝试过的:
# Using mtcars as example, e.g. first record should be "110 21 6"
dt <- data.table(mtcars)
cols <- c("hp", "mpg", "cyl")
# Works old-fashioned way
dt[, slice.verify := paste(hp, mpg, cyl)]
# Raw do.call+paste fails with message:
# Error in do.call(paste, cols): second argument must be a list
dt[, slice := do.call(paste, cols)]
# Making cols a list makes the column "hpmpgcyl" for each row
dt[, slice := do.call(paste, …