Looping through R dataframe columns

Question

I want to loop a dataframe columns and use them for something else (in this case, performing a chi-squared test on all my features.

for(i in (1:ncol(wdbc))){
  wdbc[,i]
  chisq.test(wdbc$diagnosis,wdbc[,i])
}

I've tried referring to the features in all kinds of ways, for example:

chisq.test(wdbc$diagnosis,wdbc[i]) ##looping through colnames(wdbc)

or

chisq.test(wdbc$diagnosis,wdbc$i) ##looping through colnames(wdbc)

but can't seem to solve the problem.

Answer 1

wdbc[i] will return a dataframe (rather than a vector), and wdbc$i doesn't work to loop through column names.

wdbc[,i] should work if wdbc is actually a dataframe. However, I've encountered an error in this type of situation before when my dataframe is not actually a dataframe but a tibble. The issue is that wdbc[,i] will still be a tibble rather than a vector. Try converting it to a dataframe with as.data.frame(wdbc) .