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I know that I can use sapply to find out the class of data columns like this: 

sapply(data, class)

Code above similar to: How do I get the classes of all columns in a data frame?

However, how would determine and store a vector of column names, fac that are of class factor?

Bear
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2 Answers2

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fac <- names(data)[sapply(data, is.factor)]

Bear
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    This gives you a vector, but you mentioned you want a list. You can also try `as.list(names(data)[sapply(data, is.factor)])` unless vector is what you really wanted :) – AntoniosK Sep 13 '18 at 21:50
  • @AntoniosK thank you for the catch, I meant `vector`. Corrected! – Bear Sep 13 '18 at 21:58
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Another similar way would be to use purrr package:

names(iris)[purrr::map_lgl(iris, is.factor)]
#"Species"

which(map_lgl(iris, is.factor) == TRUE) #this will return the column index as well.
#Species 
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AlexB
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