search for: blockof

Dear all, I have a large dataset which I hope to reduce in size, to make it more useable. I hope to do this by taking an average of each 60 x 60 blockof values and forming a new data frame out of the averaged values. How would I go about taking averages of 60 x 60 'blocks' in R, and cycling through the whole dataset, recording each calculated value in a new table/data frame? Many thanks for any advice offered. Steve