Odp: For loops in R

Hello

Sorry for the confusion
Here are additional details.

 velocity, popVar, archiveVar,pbestsVar are matrices with dimension of 

row, 2 col matrix.
I want to assign new values for each velocity[i,j] using the formula 

*0.4 * velocity[i,j] + 1 * randomvalue * (pbestsVar[i,j] - popVar[i,j]) 

* randomvalue * (archiveVar[random(1..500), j] -popVar[i,j]) *

with each random value different for each i j pair.

I want to do this without using the double for loops. I read somewhere 

for loops take longer to execute in R. So I want to eliminate them for
improved performance.

Long time C user and still adjusting to the R structures.

thanks for your help :)
On Mon, Jan 18, 2010 at 4:28 PM, Petr Pikal [via R] <

wrote:

Hi

Definitely not

from first I get

gBest<-floor(runif(popsize,min=1,max=top))

Error in runif(popsize, min = 1, max = top) : object 'popsize' not 

and from second

for (i in 1:popsize) {

+   for (j in 1:maxvar) {
+    gBest<-sample(top,size=1)
+    velocity[i,j]<<-.4* velocity[i,j] + 1 * runif(1) * 

+ popVar[i,j]) + 1 * runif(1) * (archiveVar[gBest,j] - popVar[i,j])
+    #velocity[i,j]<-.4* velocity[i,j] + 1 * .3722 * (pbestsVar[i,j] -
+ popVar[i,j]) + 1 * .3722 * (archiveVar[3,j] - popVar[i,j])
Error: unexpected ')' in:
"   #velocity[i,j]<-.4* velocity[i,j] + 1 * .3722 * (pbestsVar[i,j] -
popVar[i,j])"

If you by chance have all data necessary for those codes not to give 

stupid errors you could transfer their output to different objects and
check those objects if they are equivalent.

?all.equal

Regards
Petr


[hidden email]<

napsal dne 17.01.2010 08:17:16:

Hello.

I've just started using R and am trying to figure out if the two 

snippets below have the same output

gBest<-floor(runif(popsize,min=1,max=top))
velocity[i,j]<<-.4* velocity[i,j] + 1 * runif(1) * (pbestsVar[i,j] -
popVar[i,j]) + 1 * runif(1) * (archiveVar[gBest,j] - popVar[i,j])

and

for (i in 1:popsize) {
      for (j in 1:maxvar) {
         gBest<-sample(top,size=1)
         velocity[i,j]<<-.4* velocity[i,j] + 1 * runif(1) *

(pbestsVar[i,j] -

popVar[i,j]) + 1 * runif(1) * (archiveVar[gBest,j] - popVar[i,j])
         #velocity[i,j]<-.4* velocity[i,j] + 1 * .3722 * 

-

popVar[i,j]) + 1 * .3722 * (archiveVar[3,j] - popVar[i,j])
      }

many thanks


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