I tried to use the affy package (version 0.7) to analyze a set of hybs for which I masked all the features in the cel file for a few genes. When I normalize the data using the normalize method I get the following error: > data <- ReadAffy(CDFfile="HG_U95Av2.CDF", CELfiles=cels, chip.names=names, rm.mask=T, verbose=F) > ndata <- normalize(data, method="quantile", verbose=F) Error in as.vector(data) : NA/NaN/Inf in foreign function call (arg 1) Execution halted Can anybody help me? Isaac