# tapply and weighted means

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## tapply and weighted means

 I' m trying to compute weighted mean on different groups but it only returns NA. If I use the following data.frame truc: x  y  w 1  1  1 1  2  2 1  3  1 1  4  2 0  2  1 0  3  2 0  4  1 0  5  1 where x is a factor, and then use the command : tapply(truc\$y,list(truc\$x),wtd.mean, weights=truc\$w) I just get NA. What's the problem ? What can I do ? ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
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## Re: tapply and weighted means

 you need also to split the 'w' column, for each level of 'x'; you could use: lapply(split(truc, truc\$x), function(z) weighted.mean(z\$y, z\$w)) I hope it helps. Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://www.med.kuleuven.be/biostat/     http://www.student.kuleuven.be/~m0390867/dimitris.htm----- Original Message ----- From: "Florent Bresson" <[hidden email]> To: "R-help" <[hidden email]> Sent: Thursday, January 12, 2006 3:44 PM Subject: [R] tapply and weighted means > I' m trying to compute weighted mean on different > groups but it only returns NA. If I use the following > data.frame truc: > > x  y  w > 1  1  1 > 1  2  2 > 1  3  1 > 1  4  2 > 0  2  1 > 0  3  2 > 0  4  1 > 0  5  1 > > where x is a factor, and then use the command : > > tapply(truc\$y,list(truc\$x),wtd.mean, weights=truc\$w) > > I just get NA. What's the problem ? What can I do ? > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help> PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html> Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide! http://www.R-project.org/posting-guide.html