How to deal with integer(0) vectors being used as indices in a matrix

user_17974332 0
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I have a data frame A and a vector b.

I want to eliminate any columns in A with indices that are in b by doing A[,-b]

Sometimes vector b has length 0. In this case I would like the whole of data frame A to be returned. Instead I get this error:

data frame with 0 columns and 1259 rows

How can I make sure this doesn't happen in this case?

dataframe r
2 Answers

You could use setdiff():

A[, setdiff(1:ncol(A), b)]

This method can handle

  • b <- NA
  • b <- NULL
  • b <- integer(0)

and returns the entire data A.

user_100689850

Any reason a control statement won't work? Most of the time there's no need to over-complicate things. It also makes it simple for other people who may need to read or edit your code.

ret_a = function(A, b) {
    if (length(b) == 0) {
        A
    } else {
        A[,-b]
    }
}
user_57847570
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