HI Steve, I've checked the random forest package. The VariableImportance does exactly what I need. Thank you so much!
Gabriela > -----Original Message----- > From: Steven McKinney [mailto:[EMAIL PROTECTED] > Sent: Tuesday, September 09, 2008 8:48 PM > To: Gabriela Bucini; r-help@r-project.org > Subject: RE: [R] bootstrapping - number of items to replace is not a > multiple of replacement length > > > Hello, > > Your theta() function is returning different > sets of coefficients depending on the results of > step(). > > You'll need to add code to theta() to figure > out which variables were selected, and store > them into the right positions of a vector > of length 20 (the apparent number of covariates > you describe below), so that your theta() > function always returns the same sized output. > > (Google > > stepwise regression random forest > > and you'll get a number of hits > about using random forests instead > of stepwise regression, and pointers > about bootstrapping the random forest.) > > HTH > > Steve McKinney > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] > > On Behalf Of Gabriela Bucini > > Sent: Tuesday, September 09, 2008 5:02 PM > > To: r-help@r-project.org > > Subject: [R] bootstrapping - number of items to replace is not a > multiple > > ofreplacement length > > > > Hello, > > > > I'm new to boostrapping and I'd need some help to understand the error > > message that pops up when I run my script. > > > > I have a data.frame with 73 lines and 21 column. > > I am running a stepwise regression to find the best model using the R > > function "step". > > I apply bootstrapping to obtain model coefficients. > > This is my script: > > > > # "datare80" is the name of the data.frame and "woodycover" is the > > response > > variable > > theta <- function(datare80, indices) { > > d <- datare80[indices, ] # allows boot to select > subsample > > datasets > > full <- lm(d$woodycover~ ., data= d ) > > lmbroadst <- step(full, data=d , direction = "both", k=2, > > trace=0) > > coefficients(lmbroadst) # return coef. vector > > } > > resb <- boot(data = datare80, statistic = theta, R=1000) > > > > > > > > When I run it, I get these two messages: > > If I omit the last line "coefficients(lmbroadst)" in the function > > definition, I get : > > "Error in t.star[r, ] <- statistic(data, i[r, ], ...) : > > incorrect number of subscripts on matrix" > > If I have the last line "coefficients(lmbroadst)", then I get: > > "Error in t.star[r, ] <- statistic(data, i[r, ], ...) : > > number of items to replace is not a multiple of replacement > > length" > > > > > > Thank you very much for any help! > > > > Gabriela > > > > ______________________________________________ > > R-help@r-project.org mailing list > > 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. > > ______________________________________________ R-help@r-project.org mailing list 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.
