[R-sig-Geo] merging tables by columns AND row names (coordinates)

[isidora k]

Hi everyone!
I have 100 tables of the form:
XCOORD,YCOORD,OBSERVATION
27.47500,42.52641,177
27.48788,42.52641,177
27.50075,42.52641,179
27.51362,42.52641,178
27.52650,42.52641,180
27.53937,42.52641,178
27.55225,42.52641,181
27.56512,42.52641,177
27.57800,42.52641,181
27.59087,42.52641,181
27.60375,42.52641,180
27.61662,42.52641,181
..., ..., ...
with approximately 1000000 observations for each. All
these tables have the same xcoord and ycoord and I
would like to get a table of the form
XCOORD,YCOORD,OBSERVATION1,OBSERVATION2,... 
27.47500,42.52641,177,233,...
27.48788,42.52641,177,345,...
27.50075,42.52641,179,233,...
27.51362,42.52641,178,123,...
27.52650,42.52641,180,178,...
27.53937,42.52641,178,...,...
27.55225,42.52641,181,...
27.56512,42.52641,177,...
27.57800,42.52641,181,...
27.59087,42.52641,181,...
27.60375,42.52641,180,...
27.61662,42.52641,181,...
In other words I would like to merge all the tables
taking into account the common row names of their
xcoords AND ycoords.
Not all tables have the same number of observations
which means that not all pairs of x and y coords
match.
Is there a way to do this in R?
I would be grateful for any advice.
Many thanks
Isidora