<div dir="ltr">As just mentioned by Tim, you have to transform your vector 'a' to a matrix, and then apply summation:<div><br></div><div>tmp = sum(matrix(a,w,n)','c');<br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-09-27 16:56 GMT+09:00 Tim Wescott [via Scilab / Xcos - Mailing Lists Archives] <span dir="ltr"><<a href="/user/SendEmail.jtp?type=node&node=4034646&i=0" target="_top" rel="nofollow" link="external">[hidden email]</a>></span>:<br><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
OK. I think I see where I went wrong.
<br><br>There's a way to do this but it's a bit mind boggling.
<br><br>If you can let ix be a rectangular matrix of indexes, then a(ix) will be
<br>a column vector of indexed values. Then you can use 'matrix' to
<br>reassembly a(ix) into a rectangular matrix, the rows or columns of which
<br>you can sum up. I don't know if it'll be faster than the for loop,
<br>though.
<br><br>There may be an even better way of doing it, but I don't know what it
<br>is.
<br><div><div class="h5"><br>On 2016-09-27 00:28, <a href="http:///user/SendEmail.jtp?type=node&node=4034644&i=0" rel="nofollow" link="external" target="_blank">[hidden email]</a> wrote:
<div><div class='shrinkable-quote'><br>> Thanks Tim for the answer, nevertheless it cannot work.
<br>>
<br>> I want to make the sum of blocks of rows; here
<br>> - 'i' is a vector
<br>> - tmp is a vector of 20 rows in the current example
<br>> - the loop does the job, but I do not understand why the vectorization
<br>> fails ... is it a synthax error ?
<br>>
<br>> Paul
<br>>
<br>> pb: in my understanding, 'c' means 'column' and 'r' means row => for
<br>> matrix operations
<br>>
<br>>
<br>>
<br>> ----- Mail original -----
<br>> De: "Tim Wescott" <<a href="http:///user/SendEmail.jtp?type=node&node=4034644&i=1" rel="nofollow" link="external" target="_blank">[hidden email]</a>>
<br>> À: <a href="http:///user/SendEmail.jtp?type=node&node=4034644&i=2" rel="nofollow" link="external" target="_blank">[hidden email]</a>
<br>> Envoyé: Mardi 27 Septembre 2016 09:17:30
<br>> Objet: Re: [Scilab-users] is vectorization possible
<br>>
<br>> tmp = sum(a( [1 + (i-1)*n : i*n],:), 'c')
<br>>
<br>> Or sum(..., 'r'). I can't remember which is which. One makes a row,
<br>> the other makes a column, but I can never remember if it's "sum all
<br>> columns" or "sum into a column".
<br>>
<br>> On Tue, 2016-09-27 at 09:08 +0200, <a href="http:///user/SendEmail.jtp?type=node&node=4034644&i=3" rel="nofollow" link="external" target="_blank">[hidden email]</a> wrote:
<br>>> Hi All
<br>>>
<br>>> Is the vectorization possible for the example herebellow? everything I
<br>>> tried failed !
<br>>>
<br>>> Thanks for any help
<br>>>
<br>>> Paul
<br>>>
<br>>> ##############################<wbr>##############################<wbr>######
<br>>> mode(0)
<br>>>
<br>>>
<br>>> k = 100;
<br>>> a = rand(k,1);
<br>>>
<br>>>
<br>>> w = 5;
<br>>> n = (k/w);
<br>>>
<br>>>
<br>>> i = [1 : n]';
<br>>>
<br>>>
<br>>> tmp = zeros(n,1);
<br>>>
<br>>>
<br>>> // using vectorization
<br>>> tmp(i,1) = sum(a( [1 + (i-1)*n : i*n],:)
<br>>> abort
<br>>>
<br>>>
<br>>>
<br>>>
<br>>> // same using a loop
<br>>> for i = 1 : n
<br>>> tmp(i,1) = sum(a( [1 + (i-1)*w : i*w],:));
<br>>> end
<br>>>
<br>>>
<br>>> tmp
<br>>> ______________________________<wbr>_________________
<br>>> users mailing list
<br>>> <a href="http:///user/SendEmail.jtp?type=node&node=4034644&i=4" rel="nofollow" link="external" target="_blank">[hidden email]</a>
<br>>> <a href="http://lists.scilab.org/mailman/listinfo/users" rel="nofollow" link="external" target="_blank">http://lists.scilab.org/<wbr>mailman/listinfo/users</a><br>>
<br>> --
<br>>
<br>> Tim Wescott
<br>> <a href="http://www.wescottdesign.com" target="_blank" rel="nofollow" link="external">www.wescottdesign.com</a>
<br>> Control & Communications systems, circuit & software design.
<br>> Phone: <a href="tel:503.631.7815" value="+15036317815" target="_blank">503.631.7815</a>
<br>> Cell: <a href="tel:503.349.8432" value="+15033498432" target="_blank">503.349.8432</a>
<br>>
<br>>
<br>> ______________________________<wbr>_________________
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