[R] basic handling of data.frame

[Henning Meyer]

Hello,

I'm new to R but wan't to use it to compute the statistics of my medical study.
The study includes several parameters for a number of patients. Each
parameter was assessed by a number of readers, once with a special
condition, once without.
Now I have a data.frame with colums like:

PatientID, ReaderID, SpecialCond(yes/no), Parameter1, Parameter2.....

the rows are not sorted, and the table is not complete (e.g. some
readers didn't read all cases under all conditions).

What I would like to do now is for example compute Cohen's Kappa
(ckappa from package(psy)) for Parameter1 under special condition
against no special condition.
Therefore I need a table with colums:
Parameter1WithSpecial, Parameter1WithoutSpecial
And the data should be matched by PatID and ReaderID. How do I get
this kind of table?

Also how would I compute Kappa for Reader1 against Reader2?


Please help me understanding how these transformations would be done in R....


Thanks,

Henning