re shape package - use one cast() instead of many

I have a data set that I'm trying to melt and cast in a specific way using
the reshape package. (I'll use the ff_d dataset from reshape so I don't have
to post a toy data set here. )

Lets say I'm looking for the interaction of treatment with each type of
"variable" in ff_d. Using the command below gets me this. Subject will get a
column and each treatment type by each variable will also get a column with
values for each.

cast(ff_d, subject~treatment+variable)
? subject 1_potato 1_buttery 1_grassy 1_rancid 1_painty 2_potato 2_buttery
.... ?3_painty
1 ? ? ? ?3 ? ? ? 18 ? ? ? ?18 ? ? ? 18 ? ? ? 18 ? ? ? 18 ? ? ? 18 ? ? ? ?18
.... ? 18
...

Now, if I want to look at just the ?the values for each variable by subject
I can run the following command.
cast(ff_d, subject~variable)
? subject potato buttery grassy rancid painty
1 ? ? ? ?3 ? ? 54 ? ? ?54 ? ? 54 ? ? 54 ? ? 54
...

What I'm wondering now, is run one cast() call and get both of these in one
data.frame? Essentially, the values for each separate "condition" and
interactions between them? cast() doesn't let me repeat variable names as
that's what I first tried. ?Right now, i'm just running two separate cast()
calls and cbinding/merging them together. Is there a better way?

On Tue, May 5, 2009 at 3:03 PM, jwg20 <jason.gullifer at gmail.com> wrote:

I have a data set that I'm trying to melt and cast in a specific way
using
the reshape package. (I'll use the ff_d dataset from reshape so I don't
have
to post a toy data set here. )

Lets say I'm looking for the interaction of treatment with each type of
"variable" in ff_d. Using the command below gets me this. Subject will
get a
column and each treatment type by each variable will also get a column
with
values for each.

cast(ff_d, subject~treatment+variable)
? subject 1_potato 1_buttery 1_grassy 1_rancid 1_painty 2_potato
2_buttery
.... ?3_painty
1 ? ? ? ?3 ? ? ? 18 ? ? ? ?18 ? ? ? 18 ? ? ? 18 ? ? ? 18 ? ? ? 18 ? ? ?
?18
.... ? 18
...

Now, if I want to look at just the ?the values for each variable by
subject
I can run the following command.
cast(ff_d, subject~variable)
? subject potato buttery grassy rancid painty
1 ? ? ? ?3 ? ? 54 ? ? ?54 ? ? 54 ? ? 54 ? ? 54
...

What I'm wondering now, is run one cast() call and get both of these in
one
data.frame? Essentially, the values for each separate "condition" and
interactions between them? cast() doesn't let me repeat variable names as
that's what I first tried. ?Right now, i'm just running two separate
cast()
calls and cbinding/merging them together. Is there a better way?

Have a look at the margins argument.

Hadley


-- 
http://had.co.nz/

Thanks for your help! I wasn't sure what the margins variable did, but I'm
beginning to understand. I'm almost there, but with my data (and with ff_d)
I tried to margin over two variable names, however it only does one of them.
So with ff_d I set margins=c("treatment","variable"); however I only ever
get 1_(all) 2_(all) and 3_(all)... never something like (all)_painty. (This
also happens for margins=TRUE)