Dear R helpers, I have tried separate performances of background correction and normalization step by step. After I acquired the background corrected Affybatch. I expressed it for normalization using a script provided elsewhere. Finally, I acquired a normalized data matrix. However, I need to perform PMcorrection and Summarization subsequently. Due to my limited knowledge in R, I totally have no idea how to do it (At my best, I can only follow the vignette straightforwardly.) Could anyone please show me how can I perform PMcorrection and Summarization with the normalized data matrix and finally acquire expressionset? Best Regards, Kaj -- output of sessionInfo(): R version 2.15.3 (2013-03-01) Platform: x86_64-w64-mingw32/x64 (64-bit) locale: [1] LC_COLLATE=Thai_Thailand.874 LC_CTYPE=Thai_Thailand.874 [3] LC_MONETARY=Thai_Thailand.874 LC_NUMERIC=C [5] LC_TIME=Thai_Thailand.874 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] affy_1.36.1 Biobase_2.18.0 BiocGenerics_0.4.0 loaded via a namespace (and not attached): [1] affyio_1.26.0 BiocInstaller_1.8.3 preprocessCore_1.20.0 [4] zlibbioc_1.4.0 -- Sent via the guest posting facility at bioconductor.org.