R sapply is.factor

问题

I'm trying to separate a dataset into parts that have factor variables and non-factor variables.

I'm looking to do something like:

This part works:

factorCols <- sapply(df1, is.factor)
factorDf <- df1[,factorCols]

This part won't work:

nonFactorCols <- sapply(df1, !is.factor)

due to this error:

Error in !is.factor : invalid argument type

Is there a correct way to do this?

回答1:

Correct way:

nonFactorCols <- sapply(df1, function(col) !is.factor(col))
# or, more efficiently
nonFactorCols <- !sapply(df1, is.factor)
# or, even more efficiently
nonFactorCols <- !factorCols

回答2:

Joshua gave you the correct way to do it. As for why sapply(df1, !is.factor) did not work:

sapply is expecting a function. !is.factor is not a function. The bang operator returns a logical value (albeit, it cannot take is.factor as an argument).

Alternatively, you could use Negate(is.factor) which does in fact return a function.

来源：https://stackoverflow.com/questions/19169051/r-sapply-is-factor