how to append a column with different row count into a data frame in R?

Question

Suppose there is a data frame with a fixed number of row, for example

a <- as.data.frame(c(1:7))

And there is another vector with fewer (or bigger) number of row:

b <- c(1:4)

Then it is not possible to add b as new column into a:

a <- cbind(a, b)

Here is the output:

Error in data.frame(..., check.names = FALSE) : 
  arguments imply differing number of rows: 7, 4

Where the following result is expected:

1      1      1
2      2      2
3      3      3
4      4      4
5      5     NA
6      6     NA
7      7     NA

Yes, actually the problem is: data frame row count differs from new column, as you can see from the question title. — Mostafa Barmshory, May 25 '17 at 12:04

score 5 · Accepted Answer · answered May 25 '17 at 12:05

5

We can do this easily with cbind.fill from rowr

rowr::cbind.fill(a, b, fill = NA)

answered May 25 '17 at 12:05

akrun

score 3 · Answer 2 · answered May 25 '17 at 12:03

3

You can use:

a <- 1:7
b <- 1:4
n <- max(length(a), length(b))
length(a) <- n                      
length(b) <- n

df <- data.frame(cbind(a, b))

answered May 25 '17 at 12:03

Constantinos

2

The only part that you haven't copy/pasted from the dupe (`data.frame(cbind(a, b))`) is a very bad practice for data frames. – David Arenburg May 25 '17 at 12:10
Wow!! Believe it or not, I actually wrote it down from scratch! When I dont know an R function that does something, I usuallly break it down in smaller chunks and try to figure it out in base R. I didn't like `as.data.frame(c(1:7))` so I used `1:7` whereas " ... fewer (or bigger) number of row (sic)" led me to compare the lengths. Yes, it was a quick fix and probably very inefficient (but maybe not important for the lengths the poster asked for), but I've never claimed to be an expert so perhaps I'm a dupe, indeed! – Constantinos May 25 '17 at 13:11

2 Answers2