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From: sr on 12 Jul 2010 15:21
Hi Friends,

I have a matrix B of dimension (81x1541) and i'm adding +/-5% vertical perturbation to it as follows.
a=1.05;
b=0.95;
C = [a*B(:,1:40),b*B(:,41:80),a*B(:,81:120),b*B(:,121:160),a*B(:,161:200),b*B(:,201:240),...
a*B(:,241:280),b*B(:,281:320),a*B(:,321:360),b*B(:,361:400),a*B(:,401:440),...
b*B(:,441:480),a*B(:,481:520),b*B(:,521:560),a*B(:,561:600),b*B(:,601:640),a*B(:,641:680),...
b*B(:,681:720),a*B(:,721:760),b*B(:,761:800),a*B(:,801:840),b*B(:,841:880),a*B(:,881:920),...
b*B(:,921:960),a*B(:,961:1000),b*B(:,1001:1040),a*B(:,1041:1080),b*B(:,1081:1120),...
a*B(:,1121:1160),b*B(:,1161:1200),a*B(:,1201:1240),b*B(:,1241:1280),a*B(:,1281:1320),...
b*B(:,1321:1360),a*B(:,1361:1400),b*B(:,1401:1440),a*B(:,1441:1480),b*B(:,1481:1520),...
a*B(:,1521:1541)]; % perturbed model

+/-5% perturbation added to every 40 columns except in the end where i have only 20 columns left.

Is there a way to simplify this code using for loop or any other?

Thank you very much in anticipation

cheers
From: dpb on 12 Jul 2010 15:29
sr wrote:
....
> I have a matrix B of dimension (81x1541) and i'm adding +/-5% vertical
> perturbation to it as follows.
> a=1.05;
> b=0.95;
> C =
> [a*B(:,1:40),b*B(:,41:80),...

....
> +/-5% perturbation added to every 40 columns except in the end where i
> have only 20 columns left.
....

sure... :)

How many sets of 40 columns are there in the matrix B first?

doc floor % and friends may be of interest here.

Then, how many row are left over?

doc mod

How might one then loop that many times and compute the start/end
columns of the subsection to operate over on each pass? Don't forget
that last pesky group of leftovers, of course.

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