# sum all successive values in matrix row

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summyia qamar on 13 Aug 2018
Commented: summyia qamar on 13 Aug 2018
I have a vector A which represents 10 machines defect rate. Matrix B shows a process plan in each row in which the elements show process time of one part on corresponding machine for example; row 1 col 4 shows that this part takes 9 minutes to process on machine 4.I want to multiply each row of B with A such that every non zero element of B is multiplies by the sum of corresponding non zero elements of A. for example;
A=[0.1, 0.2, 0.2, 0.4, 0.2, 0.3, 0.1, 0.1, 0.1, 0.2]
B=[0 0 0 9 0 0 10 0 8 8;
8 0 0 0 7 9 0 0 0 10]
C=[0 0 0 (9+9*(0.4+0.1+0.1+0.2)) 0 0 (10+10*(0.1+0.1+0.2) 0 (8+8*(0.1+0.2)) 8+8*0.2;
(8+8*(0.1+0.2+0.3+0.2) 0 0 0 (7+7*(0.2+0.3+0.2) (9+9*(0.3+0.2)) 0 0 0 (10+10*(0.2))]
I tried cumsum and move sum but they are not giving the right answer.
summyia qamar on 13 Aug 2018
non zero elements of B are 4th, 7th 9th and 10th so these elements of A are added and multiplied with 4th element of B. then for 7th element; 7 9 and 10th elements of A are added and them multiplied with 7th element of B

Matt J on 13 Aug 2018
Edited: Matt J on 13 Aug 2018
map=(B~=0);
C=cumsum(map.*A,2,'reverse').*B+B
summyia qamar on 13 Aug 2018
yes this worked. thankyou sir

Geoff Hayes on 13 Aug 2018
summiya - for the seventh element, you seem to have
(10+10*(0.3+0.1+0.2)
Is the 0.3 a mistake and so should be 0.1 instead?
Regardless, if we assume that B has integers only, then we can determine the indices of the non-zero elements of the first row of B with
nonZeroElementsInB = B(1,:) ~= 0;
We can then determine the sum (from A) of these non-zero elements as
sumNonZeroElementsInA = sum(A(nonZeroElementsInB));
So this will be the sum of all the elements of A corresponding to non-zero elements in the first row of B
(0.4+0.1+0.1+0.2)
You will need to adjust this sum for those elements where you don't want to include all of these values.
summyia qamar on 13 Aug 2018
yes thank you for correction.I corrected 0.3 error in question