R help - May 2012 - data frame to frequencies

I have a data frame that has columns Semester, Student ID (SID), Subject,
Grade, Devel (Tor F). Students can have multiple records within a semester.
Right now, the columns are not considered factors. 

I want to do an analysis that would show the number of students who received
particular combinations of grades. I also need to distinguish between the
two Development levels (they modify classes, not students), but first things
first.
                                                        Grade
Semester      Count            A   B   C   D   F other
S1                         17               1    2    0   0   0    0
                             49                1    1    1   0   0    0
                            112               0   0    0   0   0    2
                                     etc.

I can do this procedurally but that leads to a life of trouble and ugly
code. Your help deeply appreciated to do this in a r way.


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I think you're looking for xtabs [see the examples; they're quite
good] but I can't be sure: your printed object can't really exist in R
so I'm not sure what you have currently.

Michael

On Wed, May 30, 2012 at 3:25 PM, cassiorx <cassiodorus at hotmail.com>
wrote:
> I have a data frame that has columns Semester, Student ID (SID), Subject,
> Grade, Devel (Tor F). Students can have multiple records within a semester.
> Right now, the columns are not considered factors.
>
> I want to do an analysis that would show the number of students who
received
> particular combinations of grades. I also need to distinguish between the
> two Development levels (they modify classes, not students), but first
things
> first.
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Grade
> Semester ? ? ?Count ? ? ? ? ? ?A ? B ? C ? D ? F other
> S1 ? ? ? ? ? ? ? ? ? ? ? ? 17 ? ? ? ? ? ? ? 1 ? ?2 ? ?0 ? 0 ? 0 ? ?0
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? 49 ? ? ? ? ? ? ? ?1 ? ?1 ? ?1 ? 0 ? 0 ? ?0
> ? ? ? ? ? ? ? ? ? ? ? ? ? ?112 ? ? ? ? ? ? ? 0 ? 0 ? ?0 ? 0 ? 0 ? ?2
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? etc.
>
> I can do this procedurally but that leads to a life of trouble and ugly
> code. Your help deeply appreciated to do this in a r way.
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/data-frame-to-frequencies-tp4631859.html
> Sent from the R help mailing list archive at Nabble.com.
>
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