[R] Advice on Grid Data

[Lorenzo Isella]

Dear All,
I would like to automate the analysis and plotting of data taken from a grid.
Typically I deal with 2 spatial coordinates and a scalar f(x,y), but
the spatial grid is not evenly spaced at all and usually given in this
form:
x                                 y                                     f(x,y)
0.0                      0.048979383              2.7659438106975056
0.0                      0.044986665              2.603891585041688
0.0023807306             0.04787451               2.715949356768243
0.0                      0.040993948              2.469223979694342
0.0023807306             0.043881793              2.5625191444824265
0.004761461              0.046769638              2.6629703119429022
0.0                      0.03700123               2.361940994655468
0.0023807306             0.039889075              2.436480700580665
0.004761461              0.04277692               2.517958884562618
0.0071421918             0.045664765              2.606844303834078
0.0                      0.060880877              3.470808435449538
0.0                      0.05691371               3.1907723461238686
0.0020467786             0.059650626              3.3672237912200016
0.0                      0.05294655               2.9558174712065237
0.0020467786             0.055683464              3.1075221272152054
0.004093557              0.05842038               3.268965886866726
0.0020467786             0.051716298              2.8929170062920653
0.004093557              0.054453213              3.029154848759894
0.006140336              0.057190128              3.1754081073235088
0.0                      0.02473231               2.138648866573983
0.0                      0.020556964              2.092324627395541

I tried the image plot and lattice but unsuccessfully. Now I am
reading about the sp package (
http://cran.r-project.org/src/contrib/Descriptions/sp.html ), but I
mainly would like a piece of advice about what tools to use and how to
read and plot these data (I suppose it must be common e.g. in
geography to deal with this kind of problems).
Kind Regards

Lorenzo