That error most likely indicates that abcel.data is not an AffyBatch. Did you use ReadAffy() to create abcel.data? Best, Jim James W. MacDonald Affymetrix and cDNA Microarray Core University of Michigan Cancer Center 1500 E. Medical Center Drive 7410 CCGC Ann Arbor MI 48109 734-647-5623 >>> S Peri <biocperi@yahoo.com> 07/01/04 08:25AM >>> Hello group, I am trying to normalize using expresso module and I am getting the following error. In fact I followed the example given at the bottom of help file. The following is what I get: > abcel.data.norm = expresso(abcel.data, bgcorrect.method = "rma", normalize.method = "constant", pmcorrect.method = "pmonly", summary.method = "avgdiff") background correction: rma normalization: constant PM/MM correction : pmonly expression values: avgdiff background correcting...Error in bg.correct(afbatch, method = bgcorrect.method) : No direct or inherited method for function "bg.correct" for this call Any suggestions where it is going wrong. Thank you. SP _______________________________________________ Bioconductor mailing list Bioconductor@stat.math.ethz.ch https://www.stat.math.ethz.ch/mailman/listinfo/bioconductor