[R] Re: I want to pull out an element from each of a list of matrices
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Sat Oct 14 19:26:12 CEST 2000
On Sat, 14 Oct 2000, niels Waller wrote:
> Dear colleagues,
> I suspect there is a simple answer to this question -- but I cannot find it.
> Suppose I have a list of matrices. I want to pull out an element (such as
> row 1, col 2) from each matrix. Do I need a loop to do this? Or is there an
> easy way to index this?
> Let Z denote the list of matrices. All matrices have the same order. I
> want something like
> Z[[.]][1,2] (which of course will not work, but you get the idea)
lapply(Z, function(x) x[1,2])
should do this, giving a list. Use sapply if you want a vector.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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