I have a big data.table (about 1.8M observations on 57 variables). In the original data, there's one variable with date and time as character, which I successfully converted to POSIXct. A scaled-down version of my data could be downloaded from here.
In order to obtain daily totals, I can aggregate the $value by:
exampleDF[,list(value.sum=sum(value)),by=as.Date(dateTime)]
and even by:
exampleDF[,list(value.sum=sum(value)),by=month(as.Date(dateTime))]
What I haven't been able to do is to aggregate by dateTime and another variable:
exampleDF[,list(value.sum=sum(value)),by=c("category","place")] #--This WORKS, but
exampleDF[,list(value.sum=sum(value)),by=c("category",as.Date("dateTime"))] #-- This doesn't work
I've tried many combinations using quotation marks, list, but haven't found the correct one, I'll appreciate your kind help on how to make it work.