[R] function help

Alex99 loyola9988 at yahoo.com
Fri Oct 17 17:50:07 CEST 2008

```Hi everyone,
I have dataset which I make a sample of it couple of times and each time I
get the mean and standard deviation of each row for each sample. I have a
function for that, which takes the name of the file and number of times to
sample and then returns the mean and standard deviation for each row in each
sample.

Sample=function(name, n){
res=replicate(n,name[,sample(colnames(name),n)],simplify=FALSE)

Means=do.call(rbind,lapply(res,function(x) rowMeans(x)))
rownames(Means)=paste('sample',1:n,sep="")
Gmean=colMeans(Means)

STDs=do.call(rbind,lapply(res,function(x) rowSds(x)))
rownames(STDs)=paste('sample',1:5,sep="")
Gsd=sd(STDs)

return(Gmean,Gsd)}

I then need to use the mean and standard deviation from each row to
calculate the Power for 2 sample means. here is the function I use to do it:

Power=function(alfa,m1,m2,s1,s2,n1,n2){
up=abs(m1-m2)
down=sqrt(((s1^2)/(n1))+((s2^2)/(n2)))
z=(-1)*(qnorm(1-(alfa/2)))
fi=z+(up/down)
pow=pnorm(fi)
return(pow)}

then I need to call the Power function:

Power(.05,57,mi,33,si,200,n)

the alfa,m1,s1 and n1 values are constant but the m2,s2 and n2 values are
changing.
n2 is the n used in sample function(which I could input manually)
m2 should be the grand mean for each row
s2 is the grand standard deviation for each row

example:this is a sample output for "sample" function:
\$Gmean
s1   s2   s3   s4
0.08 0.20 0.12 0.20

\$Gsd
s1        s2        s3        s4
0.2449490 0.2156741 0.2449490 0.2156741
my problem is how can I put the corresponding means and standard devotions
together  in the power function?I used a for loop, but the problem is
getting the s1...s4 from Gmean and Gsd