如何从函数参数定义r data.table/data.frame列?

编辑 :更改为OP新的可复制示例,根据OP的问题陈述提出两条建议;

library(data.table) 
DT <- data.table(ID = c("b","b","b","a","a","c"), 
                 a = 1:6, b = 7:12, c = 13:18)

colnamer1 <- function(newcolumname, datatable) {
  ## do calculations on dt
  ## create a column with whatever string is passed via 'newcolumnname'
  set(datatable, j = newcolumname, value = 42)
}

colnamer2 <- function(newcolumname, datatable) {
  ## do calculations on dt
  ## create a column with whatever string is passed via 'newcolumnname'
  dt[, (newcolumname) := 42]
}

colnamer1("name_me", DT)
colnamer2("name_me_too", DT)
DT
#    ID a  b  c name_me name_me_too
# 1:  b 1  7 13      42          42
# 2:  b 2  8 14      42          42
# 3:  b 3  9 15      42          42
# 4:  a 4 10 16      42          42
# 5:  a 5 11 17      42          42
# 6:  c 6 12 18      42          42

一个可能的 data.frame 解决方案?尽管自从采用 data.table 我的 数据帧 -ING有点生锈。当你的问题涉及到 数据帧 .

df <- data.frame(ID = c("b","b","b","a","a","c"), 
                 a = 1:6, b = 7:12, c = 13:18)
df_colnamer <- function(name_me, df) {
  new_df <- df
  new_df[[name_me]] <- 42
  new_df
}
new_df <- df_colnamer("foo", df)
new_df
#   ID a  b  c foo
# 1  b 1  7 13  42
# 2  b 2  8 14  42
# 3  b 3  9 15  42
# 4  a 4 10 16  42
# 5  a 5 11 17  42
# 6  c 6 12 18  42