I would appreciate any comments to the following question. I am trying to build a model for survival based on 155 patients and 70 covariates using lasso. Lasso picks, three variables only, say X1,X2,X3, and omits the others. I wanted to check why a particular (clinically important) variable, say X4, is omitted by lasso. One of the things I did was I ran lasso on X1,X2,X3 and X4 only. The results (coefs) I get are different from running all 70 variables, and in fact now X4 is not omitted. Why is that ? should it not be that the global (among all 70 variables) optimum, which is X1,X2,X3 and not X4, be also the local (among the four only) optimum ? Thank you for your consideration
Constantine Frangakis, PhD Professor Departments of Biostatistics Psychiatry, and Radiology Johns Hopkins University [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.