Dear list members. I am trying to make a sensitivity analysis (as derived by Zurada 1994, Engelbrecht 1995) of input parameters (gene expression data) when applying a neural network to classify different cancer subtypes. Since I am no expert in the field, (rather a newbie), I wonder if there exists an implementation in R that can be used to measure the relative importance of the input variables for the neural network. I read that the sensitivity matrix is the Jacobian matrix of the output parameters over the input parameters. I think that somehow I can grasp the concept, I just don?t know how to implement it in R. Any help, or guidelines would be greatly appreciated. Best regards Marcus

Hi, On Sep 3, 2009, at 4:40 AM, Marcus Gry wrote: > Dear list members. > > I am trying to make a sensitivity analysis (as derived by Zurada > 1994, Engelbrecht 1995) of input parameters (gene expression data) > when applying a neural network to classify different cancer > subtypes. Since I am no expert in the field, (rather a newbie), I > wonder if there exists an implementation in R that can be used to > measure the relative importance of the input variables for the > neural network. I read that the sensitivity matrix is the Jacobian > matrix of the output parameters over the input parameters. I think > that somehow I can grasp the concept, I just don?t know how to > implement it in R. Any help, or guidelines would be greatly > appreciated. First suggestion is to check out the machine learning view on cran: http://cran.r-project.org/web/views/MachineLearning.html You'll see where to get a neural network implementation there from there. Are you can calculate a jacobian matrix? Try searching the R-help list in gmane/nabble: http://www.nabble.com/forum/Search.jtp?forum=13819&local=y&query=jacob ian You might also get more help from the general R-help mailing list ... even though your specific application is related to biological data, I think your questions might be better addressed there since there somehow more general in nature. -steve -- Steve Lianoglou Graduate Student: Computational Systems Biology | Memorial Sloan-Kettering Cancer Center | Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact