Loop through and mutate multiple columns using an incrementing variable

Question

My goal is to perform multiple column operations in one line of code without hard coding the variable names.

structure(list(Subject = 1:6, Congruent_1 = c(359, 391, 384, 
316, 287, 403), Congruent_2 = c(361, 378, 322, 286, 276, 363), 
    Congruent_3 = c(342, 355, 334, 274, 297, 335), Congruent_4 = c(365, 
    503, 324, 256, 266, 388), Congruent_5 = c(335, 354, 320, 
    272, 260, 337), Incongruent_1 = c(336, 390, 402, 305, 310, 
    400), Incongruent_2 = c(366, 407, 386, 280, 243, 393), Incongruent_3 = c(323, 
    455, 317, 308, 259, 325), Incongruent_4 = c(361, 392, 357, 
    274, 342, 350), Incongruent_5 = c(300, 366, 378, 263, 258, 
    349)), row.names = c(NA, 6L), class = "data.frame")

My data looks like this.

I want need to do column subtraction and save those new values into new columns. For example, a new column by the name of selhist_1 should be computed as Incongruent_1 - Congruent_1. I tried to write a for loop that indexes the existing columns by their names and creates new columns using the same indexing variable:

for(i in 1:5)(
DP4 = mutate(DP4, as.name(paste("selhistB_",i,sep="")) = as.name(paste("Incongruent_",i,sep="")) - as.name(paste("Congruent_",i,sep="")))
)

but I received this error:

Error: unexpected '=' in: "for(i in 1:5)( DP4 = mutate(DP4, as.name(paste("selhistB_",i,sep="")) ="

I rather use this modular approach, as opposed to hard coding and writing out "selhistB = incongruent_1 - congruent_1" five times, using the mutate() function.

I also wonder if i could achieve the same goal on the long version of this data, and maybe it would make more sense.

Answer 1

As long as you are already using tidyverse packages, the following code will do exactly what you need:

library(dplyr)

for(i in 1:5){
  DP4 <- DP4 %>% mutate(UQ(sym(paste0("selhistB_",i))) := 
  UQ(sym(paste0("Incongruent_",i))) - UQ(sym(paste0("Congruent_",i))))
}

DP4

  Subject Congruent_1 Congruent_2 Congruent_3 Congruent_4 Congruent_5
1       1         359         361         342         365         335
2       2         391         378         355         503         354
3       3         384         322         334         324         320
4       4         316         286         274         256         272
5       5         287         276         297         266         260
6       6         403         363         335         388         337
  Incongruent_1 Incongruent_2 Incongruent_3 Incongruent_4 Incongruent_5
1           336           366           323           361           300
2           390           407           455           392           366
3           402           386           317           357           378
4           305           280           308           274           263
5           310           243           259           342           258
6           400           393           325           350           349
  selhistB_1 selhistB_2 selhistB_3 selhistB_4 selhistB_5
1         23         -5         19          4         35
2          1        -29       -100        111        -12
3        -18        -64         17        -33        -58
4         11          6        -34        -18          9
5        -23         33         38        -76          2
6          3        -30         10         38        -12