Hi:
Let's assume the lengths of each vector are the same so that they can
be multiplied. Here's the timing on my machine:
system.time(replicate(1000, { prob<-numeric(1000)
+
+ for (n in 1:1000) {
+ task1 <- runif(1, min=0.8, max= 0.9)
+ task2 <- runif(1, min=0.75, max= 0.85)
+ task3 <- runif(1, min=0.81, max= 0.89)
+ prob[n]<-task1*task2*task3
+ }
+ }))
user system elapsed
16.96 0.01 17.19
system.time(replicate(1000, {
+ task1 = runif(1000, min = 0.8, max = 0.9)
+ task2 <- runif(1000, min = 0.75, max = 0.85)
+ task3 <- runif(1000, min = 0.81, max = 0.89)
+ prob <- task1 * task2 * task3 } ))
user system elapsed
0.37 0.00 0.39
Dennis
On Mon, Apr 11, 2011 at 1:42 AM, Ivan Calandra
<ivan.calandra at uni-hamburg.de <mailto:ivan.calandra at uni-hamburg.de>>
wrote:
Hi,
I think you can do this without a loop (well, replicate() is based
on sapply()):
prob<-numeric(1000)
task1 <- replicate(1000,runif(1, min=0.8, max= 0.9))
task2 <- replicate(1000,runif(1, min=0.75, max= 0.85))
task3 <- replicate(1000,runif(1, min=0.81, max= 0.89))
prob <- task1*task2*task3
It might not be faster, but I don't think it can be slower. And I
find the code easier and clearer.
Please correct me if this is not equivalent.
HTH,
Ivan
Le 4/11/2011 01:06, Daniel Malter a ?crit :
The loop is correct, you just need to make sure that your
result is computed
and stored as the n-th element that is returned by the loop.
Pick up any
manual of R, and looping will be explained there. Also, I
would recommend
that you draw a random number for every iteration of the loop.
Defining the
random vectors outside the loop make sense to me only if they
are the same
length as n.
prob<-numeric(1000)
for (n in 1:1000) {
task1<- runif(1, min=0.8, max= 0.9)
task2<- runif(1, min=0.75, max= 0.85)
task3<- runif(1, min=0.81, max= 0.89)
prob[n]<-task1*task2*task3
}
If you wanted to store the individual probabilities
(task1..3), you would
proceed accordingly by defining them outside the loop and
storing the value
in the loop as the n-th element of that vector just like for prob.
HTH,
Daniel
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