I could do this in various hacky ways, but what's the right way?
I have a nice application of the by function, which does what I want. The
output looks like this:
> auc_stress
lab.samples.stress$subid: 2
cortisol amylase
1 919.05 6834.8
---------------------------------------------------------------------------------------------------------------------------
lab.samples.stress$subid: 3
cortisol amylase
11 728.25 24422.05
etc.
What I want is a data frame roughly like this:
subid cortisol.auc amylase.auc
2 919.05 6834.8
3 728.25 24422.05
etc.
What is a nice way to make that happen?
Here is the code and data that I am using, which should run directly if you
copy and paste it:
sanity.check<-read.csv("http://brainimaging.waisman.wisc.edu/~perlman/testdata.csv";,
header=TRUE, sep = ",")
lab.samples <- subset(sanity.check,Sample!='before bed' & Sample!='morning
after')
lab.samples$Sample<-factor(lab.samples$Sample)
lab.samples.stress<-subset(lab.samples,challenge=='stress')
lab.samples.control<-subset(lab.samples,challenge=='control')
auc_ground <- function(sub_df) {
print(sub_df)
auc<-sub_df[1,]*0
timedif<-c(60,10,10,10,10,10,10)
for (i in 1:(nrow(sub_df)-1) ) {
print(c(i,i+1))
#print(c(values[i],values[i+1]))
pair_area<-(sub_df[i,]+sub_df[i+1,])*timedif[i]/2
auc<-auc+pair_area
}
auc
}
auc_stress<-by(lab.samples.stress[c('cortisol','amylase')],
lab.samples.stress$subid, auc_ground, simplify=T)
auc_control<-by(lab.samples.control[c('cortisol','amylase')],
lab.samples.control$subid, auc_ground, simplify=T)
Thanks for your help!
P.S. sorry if this question has been answered before, it is nearly impossible
to get useful google results on search terms like "by"... too common word...
-dave----------------------------------------------------------------------
A neuroscientist is at the video arcade, when someone makes him a $1000 bet
on Pac-Man. He smiles, gets out his screwdriver and takes apart the Pac-Man
game. Everyone says "What are you doing?" The neuroscientist says "Well,
since we all know that Pac-Man is based on electric signals traveling
through these circuits, obviously I can understand it better than the other
guy by going straight to the source!"
______________________________________________
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.
