On Oct 5, 2010, at 8:41 AM, Alaios wrote:
Hello everyone
I need some advice if the following might be easier implemented.
There are n matrixes
each matrix needs to calculate one value for the rest n-1 matrixes
(but not for
itself). I implemented this one by
two nested loops
for (i in c(1:length(CRX))) {
for (j in c(1:length(CRX)))
if (i!=j)
# where i and j are the two indexes. If i==j then is the same matrix.
calculations()
}
Do you think there might be a more efficient R-wise way to implement
this?
Does the result of "calculations()" depend on the order of the two
selected matrices? If not, then you are doing twice as many
calculations() as necessary and could use a test like:
if (i < j) # rather than if (i != j)
You could also create 2 way combinations with the combn function, but
I don't know if that would improve the speed (and I suspect the loop
is just as fast).
What does performance profiling tell you about where most of the cpu
time is being spent?
--
David.
I would like to thank you in advance for your help
Best Regards
Alex
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