Hello,

I am using tapply to pull out data by the day of week and then perform
functions (e.g. mean). I would like to have the number of values used for
the calcuation for the functions, sorted by each day of week.  A number of
entries in any given column are NAs.

I have tried the following code and simple variants with no luck.

for (i in 1:length(a[1,])){
 x<-tapply(a[,i],a[,1],mean, na.rm=TRUE)
 amn<-tapply(a[,i],a[,1],colSums(!is.na),na.rm=T)}
Adding an explicit argument to colSums(!is.na) {e.g. colSums(!is.na(a[,i]))}
produced an error that said colSums was not a function. Trying an
imbedded tapply instead of the colSums didn't work either. Using the sum
function added the values, not the count of the values.

Thank you for any suggestions,
Stephanie

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