Hallo Christoph!
Using apply and sweep.
Both of them accept as the second argument (MARGIN) a vector which specifies the
dimension.
?apply
?sweep.
To specify the subscripts accurately I always need some trials, and to run tests, so I
cant you provide with the final solution.
Hope it helps anyway.
Sincerely Eryk.
*********** REPLY SEPARATOR ***********
On 7/20/2004 at 11:31 AM Christoph Lehmann wrote:
>>>Dear R users
>>>
>>>I have a 4-dimensional matrix (actually several 3d (x,y, slices)
>>>matrices appended over time (volumes))
>>>
>>>say, e.g. I want to z-transform the data (subtract the mean and divide
>>>by the std-deviation)
>>>
>>>for (slice in 1:slices) {
>>> for (x in 1:x.dim) {
>>> for (y in 1:y.dim) {
>>> t <- as.matrix(my.matrix[x,y,slice,1:volumes])
>>> for (vol in 1:volumes) {
>>> my.matrix.transformed[x,y,slice,vol] <-
>>>(my.matrix[x,y,slice,vol] - mean(t))/sqrt(var(t))
>>> }
>>> }
>>> }
>>>}
>>>
>>>how can I vectorize such a function using, one of the *apply functions?
>>>
>>>many thanks
>>>
>>>Cheers
>>>
>>>Christoph
>>>
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Dipl. bio-chem. Eryk Witold Wolski @ MPI-Moleculare Genetic
Ihnestrasse 63-73 14195 Berlin 'v'
tel: 0049-30-83875219 / \
mail: [EMAIL PROTECTED] ---W-W---- http://www.molgen.mpg.de/~wolski
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