Concatenate a string with integer in loop to convert columns to factor

Question

I need convert some columns of my dataset and I wish create a loop to do this instead of type line to line. But compiler show error.

Do this loop

for (i in dados_full[, 'id.' + length(12:38)]){
+   dados_full = factor(dados_full[, 'id.'+ i])
+   i =+ 1
+ }
Error in "id." + length(12:38) : non-numeric argument to binary operator

Instead of

dados_full[,"id.13"] = factor(dados_full[,"id.13"]) 
dados_full[,"id.14"] = factor(dados_full[,"id.14"]) 
dados_full[,"id.15"] = factor(dados_full[,"id.15"])
dados_full[,"id.16"] = factor(dados_full[,"id.16"]) 
dados_full[,"id.17"] = factor(dados_full[,"id.17"])

What to do?

Answer 1

We may use lapply to loop over the columns and convert to factor

nm1 <- paste0("id.", 13:17)
dados_full[nm1] <- lapply(dados_full, factor)

---

Or with dplyr

library(dplyr)
dados_full <- dados_full %>%
     mutate(across(starts_with('id.'), factor))

---

In the OP's code, the + is used for pasteing, but it wouldn't work in R. We need paste as operator+ overloading is not a case in R

nm1 <- paste("id.", 12:38)
for (nm in nm1){
   dados_full[[nm]] <-  factor(dados_full[[nm]])
  
 }