R help - Oct 2010 - loop in R

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

 

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))
u <- c(u1,u2,u3,u4,u5)
mu <- matrix(u, nrow=1000, ncol=1)
}


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]]

Hello Julia,

Your loop is just "overwriting" your variables each time.

Is this the sort of thing you want ?

# make a matrix with 10 cols of N random uniform values
N <- 5
x <- t( replicate( 10, runif(N, 0, 1) ) )

You can leave out the t( ... ) part if you want the randomizations to
be rows instead of cols

Michael


On 6 October 2010 20:51, Julia Lira <julia.lira at hotmail.co.uk>
wrote:
>
> 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
>
>
>
> 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))
> u <- c(u1,u2,u3,u4,u5)
> mu <- matrix(u, nrow=1000, ncol=1)
> }
>
>
> 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]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Is this homework?

--  
David.
On Oct 6, 2010, at 5:51 AM, Julia Lira wrote:
>
> 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
>
>
>
> 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))
> u <- c(u1,u2,u3,u4,u5)
> mu <- matrix(u, nrow=1000, ncol=1)
> }
>
>
> 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]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT

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))
> u <- c(u1,u2,u3,u4,u5)
> mu <- matrix(u, nrow=1000, ncol=1)
> }
>
>
> 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?
Yes.  You are not using the indexing variable, i,  of the for loop to change 
anything each time through the loop.
.