Understanding lattice barchart() display
On Tue, 23 Oct 2012, Peter Ehlers wrote:
As Bert correctly points out, you have more than one quant value per
tclass/stream combination. You need to summarize your 1987-case data.frame
to a 56-case data.frame (8 levels of tclass and 7 levels of stream). The
easy way to do that is:
benthos2 <- aggregate(quant ~ tclass + stream, data = benthos,
FUN = sum)
Then just use benthos2 as the data argument to barchart().
Peter, Thank you. I'll learn the aggregate function and do as you suggest. Regards, Rich