Hello, In the following code how would I get R to search the pData slot of z in order to select which columns to average? I can easily write "1:4" to select the columns but I would like to make this function more generic. In addition, if anyone can clean up the following code or point me to an easier way to do this I would greatly appreciate it. thanks, where dataset=normalized and modeled expression set; z=exprs(dataset) avg<-function(z){ x<-length(rownames(z)) y<-length(unique(pData(eset))) ii<-0 means<<-array(dim=c(x,y)) ans<-array(dim=c(x,y)) while (ii<x){ ii<-(ii+1)="" means[ii,]<<-c(mean(z[ii,1:2]),mean(z[ii,3:4]))="" ans<-means="" }}="" scott="" a.="" ochsner,="" ph.d.="" baylor="" college="" of="" medicine="" one="" baylor="" plaza,="" n810="" houston,="" tx.="" 77030="" lab="" phone:="" 713-798-1620="" office="" phone:="" 713-798-1585="" fax:="" 713-798-4161="" <="" div="">

Something like the following might help you, although I am sure there is a better way. Index1 <- which(dataset$Name_of_covariate == "Control") Also, from simpleaffy package you could try: >Control.dataset <- get.array.subset (dataset, "Name_of_covariate", "Control") David > Hello, > > In the following code how would I get R to search the pData slot of z in order to select which columns to average? I can easily write "1:4" to select the columns but I would like to make this function more generic. In addition, if anyone can clean up the following code or point me to an easier way > to do this I would greatly appreciate it. > > thanks, > > where dataset=normalized and modeled expression set; z=exprs(dataset) > avg<-function(z){ > x<-length(rownames(z)) > y<-length(unique(pData(eset))) > ii<-0 > means<<-array(dim=c(x,y)) > ans<-array(dim=c(x,y)) > while (ii<x){> ii<-(ii+1) > means[ii,]<<-c(mean(z[ii,1:2]),mean(z[ii,3:4])) > ans<-means > }} > > Scott A. Ochsner, Ph.D. > Baylor College of Medicine > One Baylor Plaza, N810 > Houston, TX. 77030 > lab phone: 713-798-1620 > office phone: 713-798-1585 > fax: 713-798-4161 > > _______________________________________________ > Bioconductor mailing list > Bioconductor at stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/bioconductor >