Hi, Has anyone written a weight function to be used with limma's read.maimages()? I tried this (based on typing wtflag): wtblank <- function(w=0.1) function(gpr){ flagged <- (gpr[,"ID"] = "BLANK") w * flagged + (!flagged) } And here are the errors I got from two different tries: > RG<-read.maimages(targets$FileName,source="genepix",columns=list(Gf="F 532 Median",Gb="B532 Median",Rf="F635 Median",Rb="B635 Median"),wt.fun=wtblank) Error in "[<-"(`*tmp*`, , i, value = function (gpr) : number of items to replace is not a multiple of replacement length > RG<-read.maimages(targets$FileName,source="genepix",columns=list(Gf="F 532 Median",Gb="B532 Median",Rf="F635 Median",Rb="B635 Median"),wt.fun=wtblank(0)) Error in w * flagged : non-numeric argument to binary operator What am I doing wrong? Thanks, G