[R] RESHAPE cast help.

[rkevinburton at charter.net]

I have a set of data that is basically sales figures for a given year. It has columns for Yeaqr, Day Of Year, Sku, SubCatetory, and Category. The first few lines of data look like:
  Year DayOfYear    Sku Quantity CatId           Category       SubCategory
1 2007         1 100091        1 10862            HOLIDAY         Christmas
2 2007         1 100138        1 11160       PET COSTUMES Famous (Licensed)
3 2007         1 100194        1 10749 HATS, WIGS & MASKS    Wigs - Women's
4 2007         1 100432        1 10865            HOLIDAY            Easter
5 2007         1 100911        1 10120                MEN   Superheroes Men

So I have the following to help me summarize the data by the various columns:

library("reshape")
t <- melt(t2007, id.var=c("DayOfYear","Category","SubCategory","Sku"), measure.var=c("Quantity"))

The following seems to give me the sales for each day of the year:

head(cast(t, DayOfYear ~ variable, sum))
  DayOfYear Quantity
1         1      861
2         2     1732
3         3     2124
4         4     1801
5         5     2147
6         6     1312

Now I want to get the sales by day of year AND category. But the following doesnt seem right:

head(cast(t, DayOfYear ~ Category ~ variable, sum))
[1] NA  2 NA NA  2 NA

For one the category name doesn't seem to be listed. I am not sure what this output shows me. Any help? Ideally I would like to have for each day of year a list of each category that a sale was made (given by the quantity, the mearsure variable)

Thank you.

Kevin