[R] Odp: loop in R
Petr PIKAL
petr.pikal at precheza.cz
Wed Oct 6 12:11:24 CEST 2010
Hi
r-help-bounces at r-project.org napsal dne 06.10.2010 11:51:37:
>
> Dear all,
>
>
>
> I need to do a loop in R, but I am not sure the software is generating
"n"
> times the variables I request differently. When I ask to print the last
matrix
> created, I just can see the loop for n=1.
>
> To be more precise, supose I need to simulate 10 times one variable and
I want
> to fit the 10 variables simulated in a matrix. I dont really know what I
am
> doing wrong, but I just can see 1 variable created.
>
> Below follows an example of what I want:
>
>
>
> rm(list=ls()) #remove almost everything in the memory
Not in memory but in file .Rdata on your PC too when you end your session
>
>
>
> set.seed(180185)
>
>
>
> #loop: create 10 times the variables (u1,u2,u3,u4,u5)
>
>
>
> for (i in 1:10){
> u1 <- c(runif(200,0,1))
> u2 <- c(runif(200,0,1))
> u3 <- c(runif(200,0,1))
> u4 <- c(runif(200,0,1))
> u5 <- c(runif(200,0,1))
Five vectors with 200 numbers each despite of excessive c() construction.
> u <- c(u1,u2,u3,u4,u5)
vector of length 1000
> mu <- matrix(u, nrow=1000, ncol=1)
changed to matrix
> }
all made 10 times. Imagine you do a loop
for (i i 10) {
copy "file1" to "file2"
}
what do you expect as a result? Ten files or only one file? When you want
a matrix with 10 colums and 1000 rows you can set it before your loop
mu <- matrix(NA, nrow=1000, ncol=10)
and use
mu[,i] <- u
as the last row in your loop. But what is wrong with
mu <- matrix(runif(10000, 0,1), nrow=1000, ncol=10)
for getting such matrix.
Regards
Petr
>
>
> As you can see, when I print(mu), I just can see a matrix with the
vector u in
> one column. I also tried to increase the number of columns to 10 (or i),
but
> the matrix will have 10 times the same vector. And what I need is like a
Monte
> Carlo simulation, where I have to simulate 10 times the variables above.
>
>
>
> Am I doing something wrong?
>
>
>
> Thanks in advance!
>
>
>
> Julia
>
> [[alternative HTML version deleted]]
>
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