Add suffix to variable value conditional on another variable - r

Question

Given the data below, what is the easiest way to add a suffix to the variable 'var' depending on the value of 'type'? So for example, if type = "white", add "_t" to the end of each value of var, and add "_b" if type = "black".
structure(list(var = c("test", "test", "score", "score", "base",
"base"), type = c("white", "black", "white", "black", "white",
"black")), row.names = c(NA, -6L), spec = structure(list(cols = list(
var = structure(list(), class = c("collector_character",
"collector")), type = structure(list(), class = c("collector_character",
"collector"))), default = structure(list(), class = c("collector_guess",
"collector")), delim = ","), class = "col_spec"), problems = <pointer: 0x0000024d0c9a2b10>, class = c("spec_tbl_df",
"tbl_df", "tbl", "data.frame"))

Answer 1

We can use dplyr::case_when():
library(tidyverse)
dat %>%
mutate(var = case_when(type == "white" ~ paste0(var, "_t"),
type == "black" ~ paste0(var, "_b"))
)
#> # A tibble: 6 × 2
#> var type
#> <chr> <chr>
#> 1 test_t white
#> 2 test_b black
#> 3 score_t white
#> 4 score_b black
#> 5 base_t white
#> 6 base_b black
data from OP
dat <- structure(list(var = c("test", "test", "score", "score", "base",
"base"),
type = c("white", "black", "white", "black", "white",
"black")),
row.names = c(NA, -6L),
class = c("spec_tbl_df", "tbl_df", "tbl", "data.frame"))
Created on 2023-02-20 with reprex v2.0.2

Answer 2

Another option with tidyverse
library(dplyr)
library(stringr)
df1 %>%
mutate(var = str_c(var, substr(str_replace(type, "^w", "t"), 1, 1), sep = '_'))
-output
# A tibble: 6 × 2
var type
<chr> <chr>
1 test_t white
2 test_b black
3 score_t white
4 score_b black
5 base_t white
6 base_b black