Loop through dataframe variables in R

Question

I have a few dataframes with only a few variables different from each other. Mostly they are the same. I would like to prepare the variables in a loop, so I do not have to specify each and every variable for all my dataframes separately. I'm however running into some issues.

clist <- c("data", "data_error", "data_RT")

I first made a list of the names of my dataframes

for (i in clist) {
i$ID <- as.factor(i$ID)
i$TMS <- as.factor(i$TMS)
i$bias<- as.numeric(i$bias)
 ... }

The I try to loop over all the variables I want to prepare. This is however not possible and I get an error message saying:

Error in i$ID : $ operator is invalid for atomic vectors

I tried google for help, but I did not understand the explanations for it :( Could you help me understand what I'm doing wrong and how I could solve it?

Answer 1

You could use a list of dataframes instead of a vector of names:

clist <- list(data, data_error, data_RT)

Then loop through the list:

for (i in 1:length(clist)) {
clist[[i]]$ID <- as.factor(clist[[i]]$ID)
clist[[i]]$TMS <- as.factor(clist[[i]]$TMS)
clist[[i]]$bias<- as.numeric(clist[[i]]$bias)
 ... }

Afterwards, you can use

list2env(clist,globalenv())

to put the dataframes back into your global environment. I would advise you to just keep them inside the list, though.