CODEWITHSUNDEEP
rdplyr
user680111
user680111

Reputation: 1011

How to paste subset of columns using dplyr

How do I paste together a dynamic subset of columns from a data.frame using dplyr?

If I have a following function:

d = data.frame(a = 1:5, b=2:6, c=3:7)

fun = function(d, colnames){

    d$f = Reduce(function(x,y)paste(x,y,sep='_'), d[,colnames])

    return(d)
}

fun(d, c('a','b'))

fun(d, c('b','c'))

fun(d, c('a','b','c'))

How do I rewrite the function using dplyr?

Upvotes: 1

Views: 952

Answers (3)

JWilliman
JWilliman

Reputation: 3883

Updated answer, use tidyr::unite!

It allows dynamic selection of columns, and has options for excluding missing values (NA) and keeping or dropping input variables.

d = data.frame(a = 1:5, b=2:6, c=3:7)

d |>
  tidyr::unite("new_col", a:c, remove = FALSE)
#>   new_col a b c
#> 1   1_2_3 1 2 3
#> 2   2_3_4 2 3 4
#> 3   3_4_5 3 4 5
#> 4   4_5_6 4 5 6
#> 5   5_6_7 5 6 7

Created on 2023-05-23 with reprex v2.0.2

Upvotes: 0

A. Suliman
A. Suliman

Reputation: 13135

Here is a version of your function using dplyr and rlang

library(dplyr)
library(rlang)

fun = function(d,a,b){
  a.var <- enquo(a)
  b.var <- enquo(b)
  d %>% mutate(f = paste(!!a.var,!!b.var, sep="_"))
}

fun(d,a,b)

Update

fun = function(d,...){
  #browser()
  vars  <- quos(...)
  d %>% mutate(f = paste(!!!vars, sep="_"))
}

fun(d,a)
fun(d,c,a)
fun(d,a,b,c)

Upvotes: 4

Stan
Stan

Reputation: 501

This works for your example:

> library(dplyr)    
> d = data.frame(a = 1:5, b=2:6, c=3:7)
> d <- d %>% mutate(f = paste(a,b,sep='_'))
> d
  a b c   f
1 1 2 3 1_2
2 2 3 4 2_3
3 3 4 5 3_4
4 4 5 6 4_5
5 5 6 7 5_6

EDIT:

After your edit, this will work for you:

> library(dplyr)
> d = data.frame(a = 1:5, b=2:6, c=3:7)
> colnames <- c("a", "c")
> d <- d %>% mutate(f = paste(!!as.name(colnames[1]),!!as.name(colnames[2]),sep='_'))     
> d
  a b c   f
1 1 2 3 1_3
2 2 3 4 2_4
3 3 4 5 3_5
4 4 5 6 4_6
5 5 6 7 5_7

Upvotes: 1

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