as.numeric() as a for loop possible?

Question

I was curious to see if there is a way to craft a for loop to do apply as.numeric() for a certain columns, since the entire DF is considered to be as a character. Perhaps I have a very large data set, and I want to make a certain column, until the very last column, to be applied.

I looked into lapply, but I think I am more confused on that.

DF =

Person	KLAS	XDXS	ASDD	BBHS	JKJA
First	Meyer	33	22	21	12
Second	Walmart	34	23	28	19
Third	Safeway	35	29	21	11
Fourth	...	...	...	...	...

Is there a way to make a for loop where I can do as.numeric() for each column, say starting at column 3 and until the very end? I would be working with large data sets, so I was wondering if there was a way to do that. Cause I dont think I can do as.numeric when there are actual characters in column 1 and 2, and using unlist() makes the problem worse.

Person <- c("First", "Second", "Third", "Fourth")
KLAS <- c("Meyer", "Walmart", "Safeway", "Kroger")
XDXS <- c("33", "34", "35", "22")
ASDD <- c("21", "28", "21", "11")
BBHS <- c("22", "23", "21", "18")
JKJA <- c("12", "19", "11", "8")
DF <- data.frame(Person, KLAS, XDXS, ASDD, BBHS, JKJA)

Is every column other than Person and KLAS desired to be numeric? — user7264, Sep 28 '22 at 23:17

score 2 · Accepted Answer · answered Sep 28 '22 at 23:19

2

You can slice only the columns you want and use apply with 2 as the second argument to apply a function along each column:

DF[, 3:ncol(DF)] <- apply(DF[, 3:ncol(DF)], 2, as.numeric)

answered Sep 28 '22 at 23:19

Xnot

171
1
3

Do not use `apply` for this. Use `lapply`. – Roland Sep 29 '22 at 05:33

score 1 · Answer 2 · answered Sep 28 '22 at 23:19

You could look into this similar question

See below code adapted from one of the answer. You can design a function to check if you can convert the column (otherwise as.numeric() will introduce NAs) and then transform your data:

library(dplyr)

is_all_numeric <- function(x) {
  !any(is.na(suppressWarnings(as.numeric(na.omit(x))))) & is.character(x)
}

DF %>%  mutate_if(is_all_numeric,as.numeric)

  Person    KLAS XDXS ASDD BBHS JKJA
1  First   Meyer   33   21   22   12
2 Second Walmart   34   28   23   19
3  Third Safeway   35   21   21   11
4 Fourth  Kroger   22   11   18    8

'data.frame':   4 obs. of  6 variables:
 $ Person: chr  "First" "Second" "Third" "Fourth"
 $ KLAS  : chr  "Meyer" "Walmart" "Safeway" "Kroger"
 $ XDXS  : num  33 34 35 22
 $ ASDD  : num  21 28 21 11
 $ BBHS  : num  22 23 21 18
 $ JKJA  : num  12 19 11 8

as.numeric() as a for loop possible?

2 Answers2