MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn moreOpportunities for recent engineering grads.

Apply Today**New to MATLAB?**

Asked by Light
on 7 Jun 2013

Now i combined answers. Help me about this iteration. I want it iterate until whole matrix zero.

A=[-1,1,1;0,-1,0;0,0,-1;1,0,0]

if ~sum(A(:)) % this iteration will be continued until whole matrix zero 0

f = find(any(A==-1,2)); % i have to find row which including only one -1, if found 2 or more, i have to pick just one of them in that iteration. How can i find it?

% in one column only one -1 and 1. then after find row with only one -1, i have to add it to the row with 1 which is staying with one column. It is the way my matrix will be zero.

2nd row which including only one -1 is added to the first row. after that:

A=[-1,0,1;0,0,0;0,0,-1;1,0,0]

If all whole matrix not zero. then will be iterated again. Please give me some clue. Help me!

Thank you for ADVICE!

*No products are associated with this question.*

Answer by Walter Roberson
on 7 Jun 2013

while true if (the ending condition is met) break end rownum = index of one row that has exactly one -1 neg1idx = column index of -1 in row number rownum plus1rownum = row index of row that has +1 in column number negidx A(plus1rownum,:) = A(plus1rownum,:) + A(rownum, :); end

It is, however, highly recommended that you add protections in case the input matrix is not structured the way you expect.

Show 1 older comment

Image Analyst
on 7 Jun 2013

A matrix could sum to zero without every element being zero. If you want every element being zero, you need to take abs() before summing, or use nnz().

Walter Roberson
on 7 Jun 2013

As I wrote in http://www.mathworks.co.uk/matlabcentral/answers/78245-check-the-matrix-result#answer_87951

~any(M(:)) will be true if M is entirely 0

Using nnz is a good idea:

nnz(M) == 0

will be true if M has only 0's in it.

Hugo
on 7 Jun 2013

Using the terminology of Walter Roberson but simpler

while ~(ending condition is met) % Include the iteration code here end

As mentioned in the previous comments, be careful with the ending condition

1) If you write

while sum(A(:)

the code will iterate until all elements of A add up to zero. This can occur, however, even if not all elements of A are zero.

2) If you write either

while sum(abs(A(:)))

or

while any(A(:))

then the code will iterate until all elements of A are zero (not just their sum).

**NOTICE** that in your comment to Walter Roberson answer, the condition if sum(A(:)) lets the iteration continue unless the sum of the elements of A is **different** from zero, which I think is not exactly what you want, or is it?

Best regards

## 2 Comments

## Light

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/78272#comment_153441

My savers it can be answered one by one.

How can i use if function to iterate it. Give me some structure please

## Walter Roberson

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/78272#comment_153465

This is a duplicate, really, of http://www.mathworks.co.uk/matlabcentral/answers/78170-matrix-problem-iterative-matrix-calculation