How do I Loop a code every 6 rows until the end?
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I need to calculate daily n-factors for a complete year. I use this code;
trapz(x(1:6,1),min(y(1:6,3),0)/trapz(x(1:6,1),min(y(1:6,2),0)
1:6 is 1st day, 7:12 is 2nd and so on... I have 1800 measurements and I need to perform this code every 6 rows from matrix Y so I have another matrix corresponding to the DAILY calculations of the n-factor.
How do I loop this code every 6 rows?
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Regards!
Sebastián.-
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Accepted Answer
Star Strider
on 23 Apr 2015
I would use the reshape function to redefine x(:,1), y(:,2) and y(:,3) as:
X1 = reshape(x(:,1), 6, []);
Y2 = reshape(y(:,2), 6, []);
Y3 = reshape(y(:,3), 6, []);
then:
for k1 = 1:size(X1,2)
W(k1) = trapz(X1(:,k1),min(Y3(:,k1),0)/trapz(X1(:,k1),min(Y3(:,k1),0))
end
There is something wrong with the code you posted, since it doesn’t make sense, so I didn’t run this code. (I assume it produces a scalar.) I will leave you to sort that out.
4 Comments
Star Strider
on 26 May 2015
Did you run the for loop? It treats every column of ‘X1’ (and ‘Y3’) as a separate vector, so there should be no problem.
More Answers (1)
Geoff Hayes
on 23 Apr 2015
Try setting the step size in your for loop to be 6. Something like the following may work where we assume that both X and Y have 1800 rows.
numRows = size(Y,1);
stepSize = 6;
for k=1:stepSize:numRows
value = trapz(X(k:k+stepSize-1,1),min(Y(k:k+stepSize-1,3),0)/...
trapz(X(k:k+stepSize-1,1),min(Y(k:k+stepSize-1,2),0);
% save value to other matrix
end
Given that stepSize is six, then our k becomes 1, 7, 13, 19, ..., 1795 and we get the correct groupings of six elements of data (since k + stepSize - 1 becomes 6, 12, 18, ..., 1800).
Try the above and see what happens!
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