# NOT RUN {
#############################################################################
# EXAMPLE 1: Group means and SDs data.ma02
#############################################################################
data( data.ma02 )
dat <- data.ma02[[1]] # select first dataset
#--- group means for read and math
GroupMean( dat[ , c("read","math") ] , group=dat$idschool )
# using rowsum
a1 <- base::rowsum( dat[ , c("read","math") ] , dat$idschool )
a2 <- base::rowsum( 1+0*dat[ , c("read","math") ] , dat$idschool )
(a1/a2)[1:10,]
# using aggregate
stats::aggregate( dat[ , c("read","math") ] , list(dat$idschool) , mean )[1:10,]
#--- extend group means to original dataset
GroupMean( dat[ , c("read","math") ] , group=dat$idschool , extend =TRUE )
# using ave
stats::ave( dat[ , "read" ] , dat$idschool )
stats::ave( dat[ , "read" ] , dat$idschool , FUN = mean )
# }
# NOT RUN {
#--- group standard deviations
GroupSD( dat[ , c("read","math") ] , group=dat$idschool)[1:10,]
# using aggregate
stats::aggregate( dat[ , c("read","math") ] , list(dat$idschool) , sd )[1:10,]
# }
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