On May 27, 2011, at 3:34 PM, sunelav wrote:
Hello,
I wrote a function that takes a matrix M and several numeric
parameters as
arguments. It returns a square matrix (same number of rows than M).
I need
to use this function n times (n>1000) with random parameters.
Just one matrix M and many parameters?
I would like to increase the speed
Loops are not necessarily slow in R. Pre-allocation of target object
size and proper use of indexing and vectorisation may add considerably
to efficient execution. In a task of this size (which I would call
"small"), it would appear to be inefficiency in the function that is
the root of your problem.
of this computation in order to increase
the size of M I can use as an input. To do so, I would like to use a
function of the apply family but I am not sure whether it is
possible in my
case. Have you got any idea ?
?mapply
mapply("f", p1, p2, p3, moreArgs=list(M=M) )
But no promises about improving on speed versus a loop.
I initially thought I could create a list containing the vectors of
the 3
random parameters and run lapply. However, in this case I don't know
how to
put M as another argument for the function.
Thank you very much for your help,
Cheers,
Sunelav.
To make things clearer; this is the loop I would like to eliminate
# the function
f=function(M,p1,p2,p3) # A matrix and 3 numeric parameters
{....
return(SM) } # a square matrix
# the Loop
SM=f(M,p1,p2,p3)
for (i in 1:10000)
{ p1=runif(..); p2=runif(..); p3=runif(..)
SM=SM+f(M,p1,p2,p3) }
View this message in context:
http://r.789695.n4.nabble.com/Use-apply-on-a-function-with-multiple-argument-including-a-matrix-tp3556193p3556193.html
David Winsemius, MD
West Hartford, CT
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