Adding multiple columns from character vector to data.table

Question

How can I add the columns a, b, c contained in new_cols to data.table df with the value NA? Preferably a nice solution without a loop.

df <- data.table(iris)
new_cols <- c("a", "b", "c")

akrun · Accepted Answer · 2021-11-26 16:52:49Z

2

The data.table syntax would be to assign (:=) the NA to the column names specified in the object 'new_cols'

library(data.table)
df[, (new_cols) := list(NA)]

-output

> head(df)
   Sepal.Length Sepal.Width Petal.Length Petal.Width Species  a  b  c
1:          5.1         3.5          1.4         0.2  setosa NA NA NA
2:          4.9         3.0          1.4         0.2  setosa NA NA NA
3:          4.7         3.2          1.3         0.2  setosa NA NA NA
4:          4.6         3.1          1.5         0.2  setosa NA NA NA
5:          5.0         3.6          1.4         0.2  setosa NA NA NA
6:          5.4         3.9          1.7         0.4  setosa NA NA NA

answered Nov 26, 2021 at 16:52

akrun

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