Matrix calculation indexing conditional

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Zeynab Mousavikhamene
评论： Andrei Bobrov 2019-8-15
I have a matrxi of 500 rows and 6 columns. I need to sum all the rows of 2nd column of the matrix if their 3rd column and 4th coumns equal to specific numbers.
How can I do that?
Lets explain more: One column is the time. An other column is radius. We can have multiple rows of the same time. Or multiple rows that have the same radius. An other coulmn is number of cells. I want to say for all times=2 and all radius=3 sum the number of cells.

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Andrei Bobrov
Andrei Bobrov 2019-8-13
编辑：Andrei Bobrov 2019-8-13
Let A - your array (500 x 6):
T = array2table(A);
T_out = varfun(@sum,T,'InputVariables',2,'GroupingVariables',3:4);
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Zeynab Mousavikhamene
Zeynab Mousavikhamene 2019-8-14
Can you explain more? Because time and radius donot have the same size.
Andrei Bobrov
Andrei Bobrov 2019-8-15
GroupCount this is numbers of the same rows in the sub-matrix of two columns - [time, radius]

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