From: Vasundhara Akkineni <vasu.akkineni_at_gmail.com>

Date: Thu 01 Dec 2005 - 15:21:02 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Dec 01 17:01:30 2005

Date: Thu 01 Dec 2005 - 15:21:02 EST

Thanks, Peter and Henrik.

Vasu.

On 11/30/05, Henrik Bengtsson <hb@maths.lth.se> wrote:

*>
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> Vasundhara Akkineni wrote:

*> > I have another issue.i have a function which calculates the log2(col i
**> > /col2) value, where i stands for columns 3,4,...etc.
**> >
**> > data<-read.table("table.txt", header=TRUE)
**> >
**> > iratio<-function(x){
**> > for(n in 3:ncol(data)){
**> > z<-log2(data[x,n]/data[x,2])
**> > }
**> > }
**> >
**> > Where x- the row number of the data frame(data).
**> >
**> > i want to store the ratios for each row in a object z, which can be
**> > accessed outside the function. How can i do this?
**>
**> Just return the result at the end of the function. Since you want to
**> return log-ratios for many pairs, I would suggest to stick them in a new
**> data frame, or since they results are all of the same data type, a
**> matrix instead. Example:
**>
**> iratio <- function(rows) {
**> # Create (pre-allocate) empty matrix poulated with NAs
**> z <- matrix(NA, nrow=length(x), ncol=ncol(data)-3+1);
**>
**> for(col in 3:ncol(data)) {
**> z[,col-3+1] <- log2(data[rows,col] / data[rows,2])
**> }
**>
**> z; # or equivalent 'return(z)'; not often seen in R code.
**> }
**>
**> You should try to look into introductions to R (sorry I don't know any
**> off hand, but just search google); this is all things you need to learn.
**> Also, you learn a lot from reading other people's code snippets.
**>
**> When you understand R better, you'll also realize that the above can be
**> done in one line of code like this:
**>
**> z <- log2(data[rows,3:ncol(data)] / data[rows,2]);
**>
**> Cheers
**>
**> Henrik
**>
**> PS. I haven't actually tested the above code in R; there might be typos.
**> DS.
**>
**> > Thanks,
**> > Vasu.
**> >
**> > [[alternative HTML version deleted]]
**> >
**> > ______________________________________________
**> > R-help@stat.math.ethz.ch mailing list
**> > https://stat.ethz.ch/mailman/listinfo/r-help
**> > PLEASE do read the posting guide!
**> http://www.R-project.org/posting-guide.html
**> >
**> >
**>
**>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Dec 01 17:01:30 2005

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