Thank you for your help.
Now let me really show my ignorance. How do I iterate through this data frame?
So with your help I have a list like
head(c)
DayOfYear Category Quantity
1 1 (Unknown) 82
2 1 7" Plates (Dessert) 4
3 1 7" Plates (Dessert) 18
4 1 9" Plates (Dinner) 10
5 1 9" Plates (Dinner) 8
6 1 ACCESSORIES & MAKEUP 127
Now I want to form another data frame for each Category. So for the above
"(Unknown)" I want to have a data.frame like:
DayOfYear Quantity
1 82
2 80
3 16
Where Quantity is obviously the quantity of "(Unknown)" category for the day of
year.
For give my ignorance I have tried c[,"(Unknown)"], c$Category["(Unknown)"],
etc and they all don't seem to work. There is something that I don't understand
about the structure that is passed back from cast. Thanks again.
Kevin
---- hadley wickham <[EMAIL PROTECTED]> wrote:
> On Tue, Aug 5, 2008 at 11:59 AM, <[EMAIL PROTECTED]> wrote:
> > 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
>
> Have a look at
>
> cast(t, DayOfYear ~ Category ~ variable, sum)
>
> it's a 3d array - probably not what you want. You probably want
>
> cast(t, DayOfYear + Category ~ variable, sum)
>
> I'd suggest reading through the introduction to reshape pdf too.
>
> Hadley
>
> --
> http://had.co.nz/
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