On Thu, October 26, 2006 18:05, Ignacio Díaz-Emparanza wrote: These sound rather easy. Unfortunately, neither Allin nor I will be able to work very much on gretl in the next few days. If anyone wants to have a go at CUSUM, the actual calculation takes place in the function cusum_test(), at line 1965 of the file lib/src/compare.c. As for the cross-correlogram, would the name "xcorrgm" suit you? Or maybe, in order to avoid command proliferation, we could revise the existing syntax of corrgm to accommodate two series instead of one. One possibility that comes to my mind is corrgm order ; y # for the ordinary correlogram corrgm order ; y x # for the cross-correlogram However, this would have the nasty side-effect of breaking existing scripts. A backward-compatible syntax could be corrgm y order x where x is an optional parameter, but it looks a bit awkward to me. Opinions? Riccardo (Jack) Lucchetti Dipartimento di Economia Facoltà di Economia "G. Fuà" Ancona