Thanks for the workaround and the explanation Alain ________________________________________ De : Milan Bouchet-Valat [nalimi...@club.fr] Date d'envoi : vendredi 28 juin 2013 19:20 À : LE TERTRE Alain Cc : 'R-help@r-project.org' Objet : Re: [R] use of formula in survey analysis with replicated weights
Le vendredi 28 juin 2013 à 17:44 +0200, LE TERTRE Alain a écrit : > Hi there, > I would like to use a formula inside a call to withReplicates in a survey > analysis. > If the initial call with formula expressed inside the function works as > expected, defining the formula outside gives an error message. > See example below, adapted from survey:withReplicates help page. > > library(survey) > library(quantreg) > > data(api) > ## one-stage cluster sample > dclus1<-svydesign( id=~dnum, weights=~pw, data=apiclus1, fpc=~fpc) > ## convert to bootstrap > bclus1<-as.svrepdesign( dclus1, type="bootstrap", replicates=100) > > ## median regression > withReplicates( bclus1, quote( coef( rq( api00~api99, tau=0.5, > weights=.weights)))) > theta SE > (Intercept) 87.78505 18.850 > api99 0.91589 0.028 > > # Defining formula outside > Myformula <- as.formula( " api00~api99") > # Rerun the same analysis > withReplicates( bclus1, quote( coef( rq( formula= Myformula, tau=0.5, > weights=.weights)))) > Erreur dans eval(expr, envir, enclos) : objet 'api00' introuvable > > # I suspect the evaluation not done in the right environment. > #If you specify with data option in rq, the initial dataframe, formula is > then correctly evaluated but .weights are not found. > > withReplicates( bclus1, quote( coef( rq( formula= Myformula, tau=0.5, > weights=.weights, data=apiclus1 )))) > Erreur dans eval(expr, envir, enclos) : objet '.weights' introuvable > > Any help greatly appreciated Here is a workaround: Myformula <- "api00 ~ api99" withReplicates(bclus1, quote(coef(rq(formula(Myformula), tau=0.5, weights=.weights)))) This solution makes sure the formula uses the environment where the weights are available. If you call as.formula() from outside the function, it will use the global environment. If you pass a character string, it will be converted to a formula object deep in a function and will thus use an environment where the weights are not be available either. Note that the same problem happens when using lm(). Regards > O__ ---- Alain Le Tertre > c/ /'_ --- Institut de Veille Sanitaire (InVS)/ Département Santé > Environnement > (*) \(*) -- Responsable de l'unité Statistiques & Outils > ~~~~~~~~~~ - 12 rue du val d'Osne > 94415 Saint Maurice cedex FRANCE > Voice: 33 1 41 79 67 62 Fax: 33 1 41 79 67 68 > email: a.leter...@invs.sante.fr > > > ______________________________________________ > 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.