I want to sum up specific array in a matrix

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Bhagya Lakshmi Marella
评论： KALYAN ACHARJYA 2019-6-24
For example If I have a matrix like this
x = [ 2.356 37
1.351 39
4.394 37
3.622 39
4.489 39
3.135 37
6.653 39 ]
I want to sum up the values that are specific to 37 and 39 seperatly only if it is alternative. If 39 and 37 are not alternative like in 4th and 5 th row wants to add that to the next subsecuent value in this case it is 37.
Some of the 37 should be (2.356+4.394+4.489+3.135), 39 should be (1.351+3.622+6.653). Please help in getting a matlab code for this!
Thank you in advance
  3 个评论
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Bhagya Lakshmi Marella
Bhagya Lakshmi Marella 2019-6-22
sum_37 should be =2.356+4.394+4.489+3.135
sum_39 should be =1.351+3.622+3.5147+3.6058+2.827+3.6134+6.653
Bhagya Lakshmi Marella
Bhagya Lakshmi Marella 2019-6-24
sum_37 should be =2.356+4.394+4.489+3.135
sum_39 should be =1.351+3.622+3.5147+3.6058+2.827+3.6134+6.653
Please help me to get this!

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采纳的回答

Shwetank Shrey
Shwetank Shrey 2019-6-24
Hope this helps you.
function [sum_37, sum_39] = compute_sum(x)
sum_37 = 0;
sum_39 = 0;
found_37 = false;
found_39 = false;
for i = 1 : length(x)
if x(i, 2) == 37
if ~found_37
sum_37 = sum_37 + x(i, 1);
found_37 = true;
found_39 = false;
else
sum_39 = sum_39 + x(i, 1);
end
else
if ~found_39
sum_39 = sum_39 + x(i, 1);
found_39 = true;
found_37 = false;
else
sum_37 = sum_37 + x(i, 1);
end
end
end
end

更多回答（1 个）

KALYAN ACHARJYA
KALYAN ACHARJYA 2019-6-22
编辑：KALYAN ACHARJYA 2019-6-22
x =[2.356 37
1.351 39
4.394 37
3.622 39
4.489 39
3.135 37
6.653 39]
idx=(find(x(:,2)==37))';
sum_37=0;
for i=1:length(idx)
sum_37=sum_37+x(idx(i),1);
end
% You can do the same for 39 too
Wait I am providing the same without loop
idx=(find(x(:,2)==37))';
sum_37=sum(x(idx(:),1));
For 39:
idx=(find(x(:,2)==39))';
sum_39=sum(x(idx(:),1));
  2 个评论
Bhagya Lakshmi Marella
Bhagya Lakshmi Marella 2019-6-22
Thank you so much!
This works to add up the elements that are specific to a 37 and 39. But, If 39 and 37 are not alternative like in 4th and 5 th row, I want to add that to the next subsecuent value in this case 4.489 should be added to 37.
KALYAN ACHARJYA
KALYAN ACHARJYA 2019-6-24
You can do that using 1/2 line of logical statments and index comparision.

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