as.numeric on subset of dataframe

Question

How can I convert columns 1 and 2 to numeric? I tried this which seemed obvious to me, but wasn't.

Thanks

df <- data.frame(v1 = c(1,2,'x',4,5,6), v2 = c(1,2,'x',4,5,6), v3 = c(1,2,3,4,5,6), stringsAsFactors = FALSE)
as.numeric(df[,1:2])

`df[1:2] <- lapply(df[1:2], as.numeric)` – akrun Apr 25 '16 at 12:07 — akrun, Apr 25 '16 at 12:07
`df[, 1:2] <- as.numeric(as.matrix(df[, 1:2]))` – jogo Apr 25 '16 at 12:14 — jogo, Apr 25 '16 at 12:14

score 3 · Answer 1 · answered Apr 25 '16 at 12:20

3

We can use lapply to loop over the columns of interest and convert to numeric

 df[1:2] <- lapply(df[1:2], as.numeric)

answered Apr 25 '16 at 12:20

akrun

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score 0 · Answer 2 · edited May 23 '17 at 10:28

I suggest this approach, using unlist. I particularly like the "one line" approach, when possible.And for more options and references, I strongly suggest this beautiful post.

 df <- data.frame(v1 = c(1,2,'x',4,5,6), v2 = c(1,2,'x',4,5,6), 
 v3 = (1,2,3,4,5,6), stringsAsFactors = FALSE)

 df[, c("v1","v2")] <- as.numeric(as.character(unlist(df[, c("v1","v2")])))
 Warning message:
 NAs introduced by coercion 

 str(df)
 data.frame':   6 obs. of  3 variables:
  $ v1: num  1 2 NA 4 5 6
  $ v2: num  1 2 NA 4 5 6
  $ v3: num  1 2 3 4 5 6

score 0 · Answer 3 · answered Apr 25 '16 at 12:57

0

You can use matrix indexing without any hidden loops:

df[, 1:2] <- as.numeric(as.matrix(df[, 1:2]))

answered Apr 25 '16 at 12:57

jogo

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as.numeric on subset of dataframe

3 Answers3