Re: [Gretl-devel] convolve function into extra?

Am 20.03.2019 um 16:39 schrieb Allin Cottrell: > On Wed, 20 Mar 2019, Sven Schreiber wrote: > >> Am 20.03.2019 um 02:05 schrieb Allin Cottrell: >>> On Tue, 19 Mar 2019, Allin Cottrell wrote: >> >>>> >>>> for p = the degree of the polynomial. >>> >>> Notation can be a bugger, and not wanting to be excessively pedantic >>> here, but is it a problem in the cheatsheet exposition that 'p' is >>> implicitly used to refer to both an array of coefficients and the length >>> of that array? >> >> In principle yes and it could be changed in one go. However, there I >> think the context is clear and one could say, the first p is in italics >> and the second one in typewriter font, so not exactly the same. > > I've tried a modification of the cheat sheet text -- please check that I > haven't messed things up! You write $r_k = \sum_{i=0}^k p_i q_{k-i}$ and I think that's basically correct. Perhaps it's useful to clarify that within the sum it must also hold $i \leq m$ and $k-i \leq n$ (equivalently $i \geq k-n$) because otherwise the coefficients are zero; such that the sum index runs from max(k-n, 0) to m, I believe.