[R] Pattern recognition

[S Peri]

Dear group, 
 
A data matrix when plotted as a line plot, I see
several 
patterns. For example, how my students performed for
different courses they took this academic year. I need
to find out a pattern divided into three categories...
say excellent, mediocral and worst.  How can I be able
to fix a threshold and seperate the patterns into
these 3 categories. The question being asked is:
I want to pick those students who are exceptionally
good in a course and exceptionally bad in a course
(here 2 bins) and third category being, for a given
course i did not see any students who performed either
good or bad (pretty much a straight line or all
students behave the same way).

my question is Can I do this in R. If so, would you
please suggest some good tutorials, considering the
fact that i am not a statistician.

The arbitarary matrix is:
a,b,c,d - On X-axis
Stu. 1 - 5 : on Y-axis,


	Stu1   stu2    stu3   stu4     stu5
a	1	2	7	3	2
b	2	2	3	2	3
c	2	1	2	3	2
d	1	2	6	2	1


Thanks
P.