[R] aggregate slow with many rows - alternative?

[Frank E Harrell Jr]

Gabor Grothendieck wrote:
> Convert dat to a matrix and see if working with the
> matrix instead of a data frame speeds things up
> enough.

In the Hmisc package the asNumericMatrix and matrix2dataFrame functions 
facilite this.

Also look at the summarize and mApply functions in Hmisc, which can be 
quite fast.

Frank Harrell