Hello,
1. After I generate a 100x50 matrix by x3<-matrix(0,100,50);for (i in
1:100) {x1<-rpois(50, mu[i]);x2<-x1; x2[runif(50)<.01]<-0;
x3[i,]<-x2},
2. I want to calculate means and sample variances of each row and create a
new matrix 100x2;
3. I then want to repeat above procedure 500 times so that eventually I
will have 500 100x2 matrices.
Would someone mind helping me to code 2 & 3?
Thanks ahead of time.
Heyen
On Wed, 18 Feb 2004, Haiyan Chen wrote:> Hello, > > 1. After I generate a 100x50 matrix by x3<-matrix(0,100,50);for (i in > 1:100) {x1<-rpois(50, mu[i]);x2<-x1; x2[runif(50)<.01]<-0; x3[i,]<-x2},YOu can do this without the loop, eg x3<-rpois(50*100, rep(mu,each=100)) x3<-ifelse(runif(50*100)<0.01, 0, x3) x3<-matrix(x3, ncol=50)> 2. I want to calculate means and sample variances of each row and create a > new matrix 100x2;means<-apply(x3,2,mean) vars<-apply(x3,2,var) cbind(means,vars)> 3. I then want to repeat above procedure 500 times so that eventually I > will have 500 100x2 matrices.make.a.matrix<-function(...){ x3<-rpois(50*100, rep(mu,each=100)) x3<-ifelse(runif(50*100)<0.01, 0, x3) x3<-matrix(x3, ncol=50) cbind(apply(x3,2,mean), apply(x3,2, var)) } many.matrices<-lapply(1:500, make.a.matrix) gives a list of 500 matrices. This isn't quite the most efficient solution, but it's not bad. -thomas
The command ?apply will easily get row means/vars (or col means/vars)
e.g.
my.mat<-matrix(rnorm(144),12)
my.mat
apply(my.mat,1,mean,na.rm=T)
apply(my.mat,1,var,na.rm=T)
The functions ?rbind and ?cbind will help you add rows or columns to
matrices or data frames
Enjoy
Wayne
-----Original Message-----
From: Haiyan Chen [mailto:hxc05@health.state.ny.us]
Sent: 18 February 2004 15:39
To: R-help@stat.math.ethz.ch
Subject: [R] How to repeat a procedure
Hello,
1. After I generate a 100x50 matrix by x3<-matrix(0,100,50);for (i in
1:100) {x1<-rpois(50, mu[i]);x2<-x1; x2[runif(50)<.01]<-0;
x3[i,]<-x2},
2. I want to calculate means and sample variances of each row and create a
new matrix 100x2;
3. I then want to repeat above procedure 500 times so that eventually I
will have 500 100x2 matrices.
Would someone mind helping me to code 2 & 3?
Thanks ahead of time.
Heyen
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Haiyan Chen wrote:>Hello, > >1. After I generate a 100x50 matrix by x3<-matrix(0,100,50);for (i in >1:100) {x1<-rpois(50, mu[i]);x2<-x1; x2[runif(50)<.01]<-0; x3[i,]<-x2}, > > >2. I want to calculate means and sample variances of each row and create a >new matrix 100x2; >Try: mean.var<-function(n=10, m=5){ mu<-(1:n)^2 x<-matrix(rpois(n*m,mu),n,m) stat<-t(apply(x,1,function(x)c(mean(x),var(x)))) } to set some elements of x to zero you can add an additional line in mean.var>3. I then want to repeat above procedure 500 times so that eventually I >will have 500 100x2 matrices. >n<-100; m<-50 n.comp<-500 for(i in 1:n.comp) eval(parse(text=paste("result",i,"<-mean.var(n,m)",sep=""))) Peter>Would someone mind helping me to code 2 & 3? > >Thanks ahead of time. > >Heyen > >______________________________________________ >R-help at stat.math.ethz.ch mailing list >https://www.stat.math.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > >
Thanks, Patrick. I was aware of that and was able to fix it.
Thanks Tom, Wayne and Peter for all your help.
Heyen
Patrick Burns
<pburns at pburns.se To: Thomas Lumley
<tlumley at u.washington.edu>
anet.com> cc: Haiyan Chen
<hxc05 at health.state.ny.us>, R-help at stat.math.ethz.ch
Subject: Re: [R] How to repeat a
procedure
02/18/2004 01:09
PM
I believe that Thomas got "mu" wrong. If I understand
correctly, the line:
x3 <- rpois(50 * 100, rep(mu, each=100))
should read:
x3 <- rpois(50 * 100, rep(mu, 50))
or just
x3 <- rpois(50 * 100, mu)
Patrick Burns
Burns Statistics
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")
Thomas Lumley wrote:
>On Wed, 18 Feb 2004, Haiyan Chen wrote:
>
>
>
>>Hello,
>>
>>1. After I generate a 100x50 matrix by x3<-matrix(0,100,50);for (i in
>>1:100) {x1<-rpois(50, mu[i]);x2<-x1; x2[runif(50)<.01]<-0;
x3[i,]<-x2},
>>
>>
>
>YOu can do this without the loop, eg
>
>x3<-rpois(50*100, rep(mu,each=100))
>x3<-ifelse(runif(50*100)<0.01, 0, x3)
>x3<-matrix(x3, ncol=50)
>
>
>
>>2. I want to calculate means and sample variances of each row and create
a>>new matrix 100x2;
>>
>>
>
>means<-apply(x3,2,mean)
>vars<-apply(x3,2,var)
>cbind(means,vars)
>
>
>
>>3. I then want to repeat above procedure 500 times so that eventually I
>>will have 500 100x2 matrices.
>>
>>
>
>make.a.matrix<-function(...){
> x3<-ifelse(runif(50*100)<0.01, 0, x3)
> x3<-matrix(x3, ncol=50)
> cbind(apply(x3,2,mean), apply(x3,2, var))
>}
>
>many.matrices<-lapply(1:500, make.a.matrix)
>
>gives a list of 500 matrices. This isn't quite the most efficient
>solution, but it's not bad.
>
>
> -thomas
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html>
>
>
>