Hi to all, I want to perform multiple regression analysis, to see if expression of some miRs could influence growth agar (as number of cells) in a group of cell lines. I've imported log2 expression data from previous array analysis for miRs, and I log2 transformed number of cells. I can calculate linear regression with lm, and I used same procedure for multiple regression, as follow: matrix <- read.table("expression_file.txt", header = TRUE, sep = "\t") attach(matrix) miRs = cbind(miR-1, miR-2, miR-3, miR-4, miR-x) agar_log = cbind(log2_n_colonies) model = lm(agar_log ~ miRs) summary(model) Do you know if lm can also perform the so-called (i) fit all (ii) stepwise regression or (iii) backward regression methods to calculate most significant model? Do you know if others packages can do it? I'm pretty new to Bioconductor and I didn't find how to do this analysis. Thanks in advance, Andrea Dr. Andrea Grilli andrea.grilli at ior.it phone 051/63.66.756 Laboratory of Experimental Oncology Rizzoli Orthopaedic Institute Codivilla Putti Research Center via di Barbiano 1/10 40136 - Bologna - Italy