[R] Re: I want to pull out an element from each of a list of matrices
Bill.Venables at cmis.csiro.au
Sun Oct 15 20:30:27 CEST 2000
At 18:26 14/10/00 +0100, Prof Brian D Ripley wrote:
>On Sat, 14 Oct 2000, niels Waller wrote:
>> Dear colleagues,
>> I suspect there is a simple answer to this question -- but I cannot find
>> 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
>> 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])
lapply(Z, "[", 1, 2)
if you want to use the extractor function directly. unlist() the result
for a vector of results.
>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)
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