[Rd] seq_along and rep_along

From: Hadley Wickham <hadley_at_rice.edu>
Date: Fri, 06 Jan 2012 12:31:55 -0600


Hi all,

A couple of ideas for improving seq_along:

    seq_along(mtcars, 1)
    seq_along(mtcars, 2)
    # equivalent to
    seq_len(dim(mtcars)[1])

    seq_len(dim(mtcars)[2])

  I often find myself wanting to iterate over the rows or column of a data frame, and there isn't a particularly nice idiom if you want to avoid problems with zeros - you have to use seq_len(nrow(df)) etc

  rep_along <- function(x, y) rep(x, length.out = length(y))

  possibly with more checking for the case where the lengths aren't integer multiples.

I'd be happy to submit proposed implementations/documentation if there was interest.

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

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Received on Fri 06 Jan 2012 - 18:37:03 GMT

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