Dear list member, I am having problem using filtering data using read.maimages and wt.fun (the files are genepix .gpr). I HAVE THIS FILTER: filter <- function(x) { ifforeground <- ( (x[,"% > B635+2SD"] > 70 | x[,"% > B532+2SD"] > 70) & (x[,"F635 Median - B635"] > 4 * x[,"B635 SD"]) & (x[,"F532 Median - B532"] > 4 * x[,"B532 SD"]) & x[,"F635 % Sat."] < 30 & x[,"F532 % Sat."] < 30 & x[,"Dia."] > 60 & (x[,"B635 Mean"] < (1.2 * x[,"B635 Median"]) & x[,"B532 Mean"] < (1.2 * x[,"B532 Median"])) & (x[,"Ratio of Medians (635/532)"] < (1.2 * x[,"Rgn Ratio (635/532)"]) | x[,"Ratio of Medians (635/532)"] > (0.8 * x[,"Rgn Ratio (635/532)"])) & x[,"Sum of Medians (635/532)"] > 1000 ) ifnotflag <- x$Flags >= 0 return(as.numeric(ifnotflag & ifforeground)) } WHEN I RUN THE SCRIPT BELOW, THERE IS NO PROBLEM: RG1 = read.maimages(targets, source="genepix", other.columns=list("% > B635+2SD", "% > B532+2SD","Flags")) WHEN I ADD wt.fun WITH THE ABOVE filter I GET AN ERROR MESSENGE: RG1 = read.maimages(targets, source="genepix", other.columns=list("% > B635+2SD", "% > B532+2SD","Flags"), wt.fun=filter) Error in gsub("\\.", "\\\\.", x) : input string 1 is invalid in this locale + Does anyone could help me figure out what is going on? Thanks. Giovani > sessionInfo() R version 2.9.2 (2009-08-24) i386-apple-darwin8.11.1 locale: en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] marray_1.22.0 limma_2.18.2