How to create new variables using all possible subtractions combinations of the original ones in R?

0
votes

So I have this big data set with 32 variables and I need to work with relative values of these variables using all possible subtractions among them. Ex. var1-var2...var1-var32; var3-var4...var3-var32, and so on. I'm new in R, so I would like to do this without going full manually on the process. I'm out of idea, other than doing all manually. Any help appreciated! Thanks!

Ex: df_original

id Var1 Var2 Var3
x 1 3 2
y 2 5 7

df_wanted

id Var1 Var2 Var3 Var1-Var2 Var1-Var3 Var2-Var3
x 1 3 2 -2 -1 1
y 2 5 7 -3 -5 -2
1
r

1 Answers

0
votes

You can do this combn which will create combination of columns taking 2 at a time. In combn you can apply a function to every combination where we can subtract the two columns from the dataframe and add the result as new columns.

cols <- grep('Var', names(df), value = TRUE)

new_df <- cbind(df, do.call(cbind, combn(cols, 2, function(x) {
  setNames(data.frame(df[x[1]] - df[x[2]]), paste0(x, collapse = '-'))
}, simplify = FALSE)))

new_df

#  id Var1 Var2 Var3 Var1-Var2 Var1-Var3 Var2-Var3
#1  x    1    3    2        -2        -1         1
#2  y    2    5    7        -3        -5        -2

data

df <- structure(list(id = c("x", "y"), Var1 = 1:2, Var2 = c(3L, 5L), 
    Var3 = c(2L, 7L)), class = "data.frame", row.names = c(NA, -2L))