[R] lapply and paste

Thomas Lumley tlumley at uw.edu
Wed Mar 28 21:19:24 CEST 2012

On Thu, Mar 29, 2012 at 7:44 AM, Ed Siefker <ebs15242 at gmail.com> wrote:
> Thank you, I was confused about that.  What exactly is lapply for then,
> if R handles this kind of thing automatically?  Are there functions that are
> not "vectorized"?

There are, especially ones you write yourself that don't need to be
vectorised on all their arguments.

Also, there may be more than one direction to vectorise: eg mean or
median work on vectors, but need some form of loop to work on data
frames (lapply, apply, for)

And there are structures too complicated to put in a vector: if I have
a list of linear models and want the variance-covariance matrices from
each one, lapply() is a good way to do it.


Thomas Lumley
Professor of Biostatistics
University of Auckland

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