I have a 5x6 matrix. I want to calculate sum of only those values which are consecutive nonzero along each row. How to do that? The desired result given in description box.

a = [2 3 1 4 0 0;
     0 0 0 0 0 0;
     0 0 1 5 7 0;
     0 0 0 0 4 0;
     4 5 0 0 6 8];
desired_result = [10;0;13;0;23]

desired_result = 4×1

10 0 13 0

[the cyclist]

Why is the result of the 4th row not 4? Is it because you want to have at least two non-zero values to be included?

What you should the result be for a row with two set of consecutive non-zero, such as

a = [2 3 0 5 7 0]

[Torsten]

You don't take the 4 in row 4 to conribute to the sum because it has a consecutive zero.

But then why do you take the 4 in row 1 and the 7 in row 3 to contribute to the sum ?

I would have expected desired_result to be [6 0 6 0].

[Payel]

The result of 4th row is not 4 because I want summation of only consecutive non zero values along each row.

The desired result of a should be 17

[the cyclist]

I believe a correct re-statement of the rule is, "Sum all non-zeros that are next to at least one other non-zero."

Answer 1

[the cyclist]

I believe this does what you want:

% Input
a = [2 3 1 4 0 0;
     0 0 0 0 0 0;
     0 0 1 5 7 0;
     0 0 0 0 4 0;
     4 5 0 0 6 8];

% Append columns of zeros at both ends, because we are going to check in
% the next line if an element is a "singleton" with zeros on both sides
b = [zeros(height(a),1) a zeros(height(a),1)];

% Identify the non-singleton value (i.e. the ones that do not have zeros on either side)
includeInSum = not((b(:,1:end-2) == 0) & (b(:,3:end)==0));

% Sum the values that should be included
result = sum(a.*includeInSum,2)

result = 5×1

10 0 13 0 23

Answer 2

[Image Analyst]

a = [2 3 1 4 0 0;
    0 0 0 0 0 0;
    0 0 1 5 7 0;
    0 0 0 0 4 0;
    4 5 0 0 6 8];
desired_result = [10;0;13;0;23]

desired_result = 5×1

10 0 13 0 23

desired_result = sum(a, 2)

desired_result = 5×1

10 0 13 4 23

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[Payel]

how to get the summation value of 4th row to be zero? as it is asked to find summation of only consecutive nonzero values along each row

[Image Analyst]

Row 4 has one "consecutive' value, so why not sum it in? Do you want to sum in values only if the run of non-zero values is 2 or more? See @the cyclist's answer below. Is it homework? If so you can't use it.

This looks like a homework problem. If you have any questions ask your instructor or read the link below to get started:

How do I get help on homework questions on MATLAB Answers? - MATLAB Answers - MATLAB Central

Obviously we can't give you the full solution because you're not allowed to turn in our code as your own.