crumbly - 10 months ago 53

R Question

I have the following dataframe

`u`

`u <- data.frame(a1 = c("a", "b", "c"), a2 = c(2, 1, 3))`

I want to add 14 more columns simultaneously based on a simple sequence which is to create new column by adding constant 3 to the last column.

the resulting data frame:

`a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15 a16`

a 2 5 8 11 14 17 20 23 26 29 32 35 38 41 44

b 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43

c 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45

Answer Source

I would vectorize this as follows

```
u[paste0("a", 3:16)] <- matrix(u$a2 + rep(3*1:14, each = 3), nrow = 3)
u
# a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15 a16
# 1 a 2 5 8 11 14 17 20 23 26 29 32 35 38 41 44
# 2 b 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43
# 3 c 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45
```