Thanks, let me try to clarify my question with an example.

Suppose I have the following data:

Gender,   Major,  Course-Grade
F, Psy, 3.5
F, Psy, 3.1
M, Hst, 3.7
F,  Hst,  3.6
M, Hst,  2.6
M, Eng, 3.9

I want to compute a table like the following:

X-axis: Gender
Y-axis: Major
Cell(x,y) = mean course-grade

So for example, with the data above:

          F     M
------------------------
Psy |   3.3    NA
Hst |   3.6    3.15
Eng |  NA    3.9

If I were doing this in SQL I'd do it with a cross-tab query.  But the world
of R still has much unfamiliar terrain :)

Thanks,
Christian


On 11/15/06, Jeffrey Robert Spies <jspies@nd.edu> wrote:
>
> I'm not sure I understand the question, but you might look into the
> following functions:
>
> unique
> heatmap
> image
>
> Again, if I understand the question, you would create a length(unique
> (x)) by length(unique(y)) sized matrix, and fill it with appropriate
> values of z.  Then pass that to heatmap or image.
>
> Hope that helps--feel free to tell me if I've answered  the wrong
> question,
>
> Jeff.
>
> On Nov 15, 2006, at 8:30 AM, Christian Convey wrote:
>
> > I'm very new to R, so please forgive me if I just missed the answer in
> > existing documentation...
> >
> > I have a data set with at least three columns, X, Y, and Z.
> >
> > I want to produce a chart where one axis shows all the unique
> > values of X,
> > and the other axis shows all the unique values of Y.  Each cell
> > within the
> > chart should contain the result of applying an aggregate function
> > (such as
> > mean(), for example) to Z value of those rows that are associated
> > with that
> > cell (via their X and Y values).
> >
> > Can someone recommend a good way to do this?
> >
> > Thanks very much,
> > Christian
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-
> > guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
>

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