[Gretl-devel] convolve function into extra?

Hi, while looking at the example scripts I've noticed convolve.inp, and then also the paragraph about Convolution in the guide (cheat sheet chapter, p. 154 for me). I wonder if this should be wrapped in a hansl function and added to the 'extra' addon, like this: <hansl> function void padzeros(matrix *a, matrix *b) a = vec(a) b = vec(b) outrows = rows(a) + rows(b) - 1 a |= zeros(outrows - rows(a), 1) b |= zeros(outrows - rows(b), 1) end function function matrix convolve(matrix p, matrix q) padzeros(&p, &q) return filter(p, q) end function # And for comparison only: function matrix convolve_fft(matrix p, matrix q) padzeros(&p, &q) f = fft(p ~ q) return ffti(cmult(f[,1:2], f[,3:4])) end function <hansl> As mentioned in the guide, the filter-based variant is indeed about 30% faster in my examples. BTW, I think there are some typos in the notation in the Convolution paragraph: The sum indices i should start at 0, not 1, and the upper bound for the R(x) index should be p + q - 1 instead of pq-1. Any feedback welcome. thanks, sven