On Jul 22, 2013, at 3:23 PM, David Winsemius wrote: > > On Jul 22, 2013, at 3:12 PM, Robert Lynch wrote: > >> I am trying to compute GPA from class grades(which have been normallized) >> I have for example the following matrix >> >> Master = >> SID B2A B2B B2C C2A C2B C2C C118A C118B C118C >> 001 0.01 0.5 -0.4 1.2 -1.8 0.3 -0.3 0.4 >> 0.5 >> 002 0.01 0.5 -0.4 0.5 -0.4 1.2 -1.8 0.3 >> -0.3 >> 003 0.04 0.05 0.5 -0.4 - 0.5 0.4 -1.2 1.8 >> 0.3 >> etc >> >> Where each column has a zero mean and a standard deviation of 1. I want to >> calculate a weighted average for each row(student ID) that takes into >> account that >> B2A, C118A, C118B, and C118C are all 4 unit classes, and the rest, B2B, >> B2C, C2A,C2B,C2C are 5 unit classes >> >> I have tried >> Units<-c(4,5,5,5,5,5,4,4,4) >> Master$zGPA <-weighted.means(Master[,2:10],Units) >> >> But that gets me one number and not a vector. > > Perhaps something along lines of > > Master$zGPA <-sapply( weighted.means(Master[,2:10], weighted.means, > weghts=Units) > > (Untested in absence of data or name of package from which function is > loaded.) > >> ?weighted.means > No documentation for ‘weighted.means’ in specified packages and libraries: > you could try ‘??weighted.means’
If you are using weighted.mean and want this applied by row (one row per student I guess) , then probably this would be better: Master$zGPA <- apply( Master[,2:10], 1, weighted.means, w=Units) -- David. > > --- > David Winsemius > Alameda, CA, USA > > ______________________________________________ > 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. David Winsemius Alameda, CA, USA ______________________________________________ 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.