Combine two or more columns in a dataframe into a new column with a new name

Question

For example if I have this:

n = c(2, 3, 5) 
s = c("aa", "bb", "cc") 
b = c(TRUE, FALSE, TRUE) 
df = data.frame(n, s, b)

  n  s     b
1 2 aa  TRUE
2 3 bb FALSE
3 5 cc  TRUE

Then how do I combine the two columns n and s into a new column named x such that it looks like this:

  n  s     b     x
1 2 aa  TRUE  2 aa
2 3 bb FALSE  3 bb
3 5 cc  TRUE  5 cc

Answer 1

Use paste.

 df$x <- paste(df$n,df$s)
 df
#   n  s     b    x
# 1 2 aa  TRUE 2 aa
# 2 3 bb FALSE 3 bb
# 3 5 cc  TRUE 5 cc

Answer 2

For inserting a separator:

df$x <- paste(df$n, "-", df$s)

Answer 3

As already mentioned in comments by Uwe and UseR, a general solution in the tidyverse format would be to use the command unite:

library(tidyverse)

n = c(2, 3, 5) 
s = c("aa", "bb", "cc") 
b = c(TRUE, FALSE, TRUE) 

df = data.frame(n, s, b) %>% 
  unite(x, c(n, s), sep = " ", remove = FALSE)

Answer 4

Some examples with NAs and their removal using apply

n = c(2, NA, NA) 
s = c("aa", "bb", NA) 
b = c(TRUE, FALSE, NA) 
c = c(2, 3, 5) 
d = c("aa", NA, "cc") 
e = c(TRUE, NA, TRUE) 
df = data.frame(n, s, b, c, d, e)

paste_noNA <- function(x,sep=", ") {
gsub(", " ,sep, toString(x[!is.na(x) & x!="" & x!="NA"] ) ) }

sep=" "
df$x <- apply( df[ , c(1:6) ] , 1 , paste_noNA , sep=sep)
df

Answer 5

Using dplyr::mutate:

library(dplyr)
df <- mutate(df, x = paste(n, s)) 

df 
> df
  n  s     b    x
1 2 aa  TRUE 2 aa
2 3 bb FALSE 3 bb
3 5 cc  TRUE 5 cc

Answer 6

Instead of

• paste (non-tidy),
• paste0 (defauld separator) or
• unite (constrained to 2 columns and 1 separator),

I'd suggest a more flexible anternative: stringr::str_c

library("tidyverse")
df %>% mutate(x=str_c(n,"-",s,".",b))
#> # A tibble: 3 x 4
#>       n s     b     x         
#>   <dbl> <fct> <lgl> <chr>     
#> 1     2 aa    TRUE  2-aa.TRUE 
#> 2     3 bb    FALSE 3-bb.FALSE
#> 3     5 cc    TRUE  5-cc.TRUE 

Answer 7

We can use paste0:

df$combField <- paste0(df$x, df$y)

If you do not want any padding space introduced in the concatenated field. This is more useful if you are planning to use the combined field as a unique id that represents combinations of two fields.