Asked by Hamaza24
on 17 Jun 2013

I am trying to sum every 5 rows of a column, Is my part of code right

instdec = (instdec_t+instdec_d)/2; startdec1 = (instdec >= 0.25*overalldec); startdec2=zeros(npts,1); while decpt==1 for j = 2:npts-4 startdec2(j) = sum(startdec1(j:j+4)); if startdec2(j)== 5 decpt=j-1; break end end

I keep getting wrong answers, the second row becomes 2, and everything else is zeros

I would appreciate any support since I am very new to matlab

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Answer by Andrei Bobrov
on 17 Jun 2013

Edited by Andrei Bobrov
on 17 Jun 2013

Accepted answer

startdec2 = sum(reshape([startdec1;zeros(mod(-numel(startdec1),5),1)],5,[])).';

ADD

startdec1 = rand(42,1) < .7; b = conv(startdec1,ones(5,1),'valid'); decpt = find(b == 5,1,'first')-1;

Show 2 older comments

Hamaza24
on 17 Jun 2013

I really appreciate you effort Andrei.

and yea jan, if I get you right. decpt 1 and npts is 42

but this way reduces my data as every 5 rows are summed as if I have 42 rows they will be reduced to 9

what I am looking for is to still have the full 42 rows where row 1 will be the sum of rows (1 to 5), row 2 will be sum of rows (2 to 6) and so on. till row 37 (sum of 37 till 42).

it is still bugging me, applying what i learnt from the book is giving me a headache.

Answer by Hamaza24
on 17 Jun 2013

Hi Jan and tom.

the purpose is to check if the numbers on every row exceed a certain value for a 5 successive rows.

so, the methodology I used is that if the condition of exceeding that certain number happens then generate 1, otherwise 0.

to check the of every five successive rows meet the condition, I want to sum every 5 rows and when the sum is 5 then I know that location and get its original value.

I can't really provide data tom. sorry for that and thanks for your help.

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## 2 Comments

## Jan Simon (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/79272#comment_155329

I've applied a more readable indentation. Now it is obvious that an

endis missing.The purpose of your code is not clearly explained. All we have is the code you have shown here. Then it is impossible to guess, if it satisfies your needs. Please add a detailed description of the aim of the program - by editing the original question, not as comment and not as answer. Thanks.

## Tom (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/79272#comment_155330

can you provide some example data to test with?