Summing from control variable in loop to end of loop / from beginning

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Kian 2016-5-9

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关闭： MATLAB Answer Bot 2021-8-20

I have a matrix 1738 * 2 and I want to loop through the first column. Dependent on the iteration of the loop I would like to sum up the the second column from the start value to the (control variable - 1) and from the control variable to the end of the second column. Thanks for every advice

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Answer 1

Weird Rando 2016-5-9

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编辑：Weird Rando 2016-5-9

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Don't necessary need a loop you could do something like this

startValue = 2;
control = 10;
a=[1:1:1738; 11:1:1748]';
a1 = sum(a(:,1))
a2 = sum(a(startValue:(control - 1),1))

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Kian 2016-5-9

Thanks for your answer. Unfortunately i need the loop as it is part of a bigger script. This is how i try to start with the loop through the first column - COG_Ton is the 1738 x 2 Matrix (although this is also variable on the input data). for ik = COG_Ton (:,1)

so i am looking for something like: tonnes(ik) = sum (COG_Ton (1:ik-1, 2)) and tonnes2(ik) = sum(COG_Ton (ik:end,2)) but i dont know how to write this in matlab

Weird Rando 2016-5-10

编辑：Weird Rando 2016-5-11

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I think you when wrong is when you initialise the for loop statement. It gives the COG_Ton values. So if COG_Ton(1,1) = 1024,

tonnes(1024) = sum(COG_Ton(1:1024-1,2)).

If that number exceed the length of COG_Ton you will incur an error.

Here my solution.

nloop = size(COG_Ton,1)-1;
for ik = 1:nloop
   tonnes(ik) = sum (COG_Ton (1:ik, 2));
   tonnes2(ik) = sum(COG_Ton (ik+1:end,2));
end

However if you did that, you would probably need to amend your code if there were some other code inside that for loop that uses ik and replace that as COG_Ton(ik,1).