[R] More efficient matrix computation
Wolski
wolski at molgen.mpg.de
Tue Aug 31 18:37:03 CEST 2004
Hi!
apply(m,2,quantile,c(0.95,0.99))
/Eryk
*********** REPLY SEPARATOR ***********
On 8/31/2004 at 9:16 AM JTW wrote:
>>>I have a 20x3 matrix as follows:
>>>
>>>> m <- replicate(3, matrix(rnorm(20),20,1))
>>>
>>>I need to compute, say, 95th and 99th percentiles of
>>>each column such that the resulting matrix becomes 2x3
>>>with each row representing the respective percentile.
>>>My "best effort" is to compute one column at a time as
>>>follows:
>>>
>>>> quantile(m[,1], c(0.95, 0.99))
>>>
>>>To do the same for columns 2 and 3, I would simply
>>>change the column number accordingly. Clearly, this
>>>is not very efficient as I may have a large matrix
>>>(e.g., 100,000x500) to work with. Any help with the
>>>code is appreciated.
>>>
>>>Jack Wang
>>>
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Dipl. bio-chem. Witold Eryk Wolski @ MPI-Moleculare Genetic
Ihnestrasse 63-73 14195 Berlin 'v'
tel: 0049-30-83875219 / \
mail: witek96 at users.sourceforge.net ---W-W---- http://www.molgen.mpg.de/~wolski
wolski at molgen.mpg.de
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