Re: [Gretl-devel] matrix multiplication question

Am 09/26/2011 06:48 AM, schrieb Berend Hasselman: > On 26-09-2011, at 03:09, Allin Cottrell wrote: > >> On Sun, 25 Sep 2011, Summers, Peter wrote: >> >>> Allin et al, >>> >>> <quote> >>> Proper addition is of course commutative, but the "extended >>> addition" that I'm talking about here maybe is not. I tend to think >>> of the left-hand operand as the "posit", so to speak, and the >>> right-hand operand as the increment (or decrement, in the case of >>> subtraction). And I reckon I can attach a good sense to the case >>> where an m x n matrix is the posit and the increment or decrement is >>> a scalar (applied to all elements of the posit). But I feel queasy >>> about the case where the posit is a scalar value and the >>> increment/decrement is an m x n matrix. This seems a step too far. >>> >>> This may become moot if we decide to tighten up and insist on the >>> dot operators, but I thought I'd just mention it. >>> </quote> >>> >>> My first thought is that if the manual says (mxn) + scalar is >>> allowed, then the order shouldn't matter. Addition is addition. I strongly agree here; introducing some notion of pre- or post-addition is certainly creative, but not helpful here IMHO. Apart from that, given that matrix plus scalar is a case of "broadcasting" (a term borrowed from numerical Python) as documented in the gretl user guide also for more general cases, and given that gretl in general uses ".+" as an operator to indicate the programmer's wish to do that, I tend to agree with Allin to require the use of ".+" also for the matrix plus scalar case. Certainly not for 1.9.6, but a good case for 2.0 IMHO. cheers, sven _______________________________________________ Gretl-devel mailing list Gretl-devel(a)lists.wfu.edu http://lists.wfu.edu/mailman/listinfo/gretl-devel