How to use nested loops in R to change values?

Question

I have a data set where I want all 1's to be 0's and anything over 1 to be 1's. I've tried using parentheses instead of brackets.

for (i in 1:nrow(StudentDrugs)){
  for(j in 1:ncol(StudentDrugs)){
    ifelse([i,j] == 1, 0, 1)
  }
}

I get: Error: unexpected '[' in: " for(j in 1:ncol(StudentDrugs)){ ifelse(["

Answer 1

As you didn't yet provide an example dataset, examples below use mtcars.

With base R, rapply and ifelse:

rapply(mtcars,f = function(x) ifelse(x==1,0,ifelse(x>1,1,x)),how = 'replace')

                    mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4             1   1    1  1    1  1    1  0  0    1    1
Mazda RX4 Wag         1   1    1  1    1  1    1  0  0    1    1
Datsun 710            1   1    1  1    1  1    1  0  0    1    0
Hornet 4 Drive        1   1    1  1    1  1    1  0  0    1    0
Hornet Sportabout     1   1    1  1    1  1    1  0  0    1    1
...

With dplyr and case_when.

library(dplyr)
mtcars %>% mutate(across(everything(),function(x) case_when(x==1 ~ 0, x > 1 ~ 1, T ~ x )))

                    mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4             1   1    1  1    1  1    1  0  0    1    1
Mazda RX4 Wag         1   1    1  1    1  1    1  0  0    1    1
Datsun 710            1   1    1  1    1  1    1  0  0    1    0
Hornet 4 Drive        1   1    1  1    1  1    1  0  0    1    0
Hornet Sportabout     1   1    1  1    1  1    1  0  0    1    1
...