[R] assign group letters to T/F matrix

[eldor ado]

dear R community,

i appologize as this is kind of a newbie question, but:

I want to assign group letters (like in anova post-hoc tests) to data
with combined means and SDs. It's easy to apply t-test formulas to get
a materix like

(A - D are treatments

  |  A   B   C   D
-----------------------
A|       T    F   F
B|             T   F
C|                  F
D|

where true stands for sign. differences/ F for no sign. differences.
is there an alogarithm that converts such a matrix to letters to be
assignedto A, B, C,... ? and does maybe somebody know a packages that
runs t-tests on means+SD+n data?

lukas kohl