[Scilab-users] is vectorization possible

[paul.carrico at free.fr]

Thanks Tim for the answer, nevertheless it cannot work.

I want to make the sum of blocks of rows; here 
- 'i' is a vector
- tmp is a vector of 20 rows in the current example
- the loop does the job, but I do not understand why the vectorization fails ... is it a synthax error ?

Paul

pb: in my understanding, 'c' means 'column' and 'r' means row => for matrix operations



----- Mail original -----
De: "Tim Wescott" <tim at wescottdesign.com>
À: users at lists.scilab.org
Envoyé: Mardi 27 Septembre 2016 09:17:30
Objet: Re: [Scilab-users] is vectorization possible

tmp = sum(a( [1 + (i-1)*n : i*n],:), 'c')

Or sum(..., 'r').  I can't remember which is which.  One makes a row,
the other makes a column, but I can never remember if it's "sum all
columns" or "sum into a column".

On Tue, 2016-09-27 at 09:08 +0200, paul.carrico at free.fr wrote:
> Hi All
> 
> Is the vectorization possible for the example herebellow? everything I
> tried failed !
> 
> Thanks for any help
> 
> Paul
> 
> ##################################################################
> mode(0)
> 
> 
> k = 100;
> a = rand(k,1);
> 
> 
> w = 5;
> n = (k/w);
> 
> 
> i = [1 : n]';
> 
> 
> tmp = zeros(n,1);
> 
> 
> // using vectorization
> tmp(i,1) = sum(a( [1 + (i-1)*n : i*n],:)
> abort
> 
> 
> 
> 
> // same using a loop
> for i = 1 : n
>     tmp(i,1) = sum(a( [1 + (i-1)*w : i*w],:));
> end
> 
> 
> tmp
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-- 

Tim Wescott
www.wescottdesign.com
Control & Communications systems, circuit & software design.
Phone: 503.631.7815
Cell:  503.349.8432


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