[R] apply formula over columns by subset of rows in a dataframe (to get a new dataframe)
Massimo Bressan
massimo.bressan at arpa.veneto.it
Fri May 13 13:55:39 CEST 2016
hi
I need to apply a user defined formula over some selected columns of a dataframe by subsetting group of rows (blocks) and get back a new dataframe
I’ve been managed to get the the calculations right but I’m not satisfied at all by the form of the results
please refer to my reproducible example
##########
# my user function (an example)
mynorm <- function(x) {(x - min(x, na.rm=TRUE))/(max(x, na.rm=TRUE) - min(x, na.rm=TRUE))}
# my dataframe to apply the formula by blocks
mydf<-data.frame(blocks=rep(c("a","b","c"),each=5), v1=round(runif(15,10,25),0), v2=round(rnorm(15,30,5),0))
#my attempts (not satisfied by final output)
tapply(mydf$v1, mydf$blocks, mynorm)
byf<-factor(mydf$blocks)
aggregate(mydf[2:3], list(byf), mynorm)
aggregate(mydf[2:3], list(mydf$blocks), mynorm, simplify = FALSE)
###########
please can anyone give me some hints on how to properly proceed?
I need a dataframe with all variables as final result
sorry but I’m sort of definitely stuck with this…
thanks
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