problem with using coalesce to merge 2 columns into 1

I would like to merge values from 2 columns into 1. For example, here is sample data:

id   x    y
1   12  
1         14  
2   13      
3   15 
3         18
4         19

I want

id   x    y     z
1   12          12  
1         14    14  
2   13          13 
3   15          15 
3         18    18
4         19    19

I tried using coalesce to create a new variable.

coalesce <- function(...) {
  apply(cbind(...), 1, function(x) {
    x[which(!is.na(x))[1]]
  })
}

df$z <- coalesce(df$x, df$y)

However, the variable doesn’t reflect the columns joined. Am I using this function incorrectly?

>Solution :

You could use the dplyr::coalesce function:

> df$z <- dplyr::coalesce(ifelse(df$x == "", NA, df$x), df$y)
> df
  id  x  y  z
1  1 12    12
2  1    14 14
3  2 13    13
4  3 15    15
5  3    18 18
6  4    19 19
> 

To implement my own mycoalesce:

mycoalesce <- function(...) {apply(cbind(...), 1, max)}

And:

> df$z <- mycoalesce(df$x, df$y)
> df
  id  x  y  z
1  1 12    12
2  1    14 14
3  2 13    13
4  3 15    15
5  3    18 18
6  4    19 19
>