How can i make the sum of matrix elements>0 under the condition that there are min 3 zeros between the sums?

I hava a matrix: a=[2 3 0 0 4; 0 0 0 0 0; 0 5 3 0 4; 14 4 0 1 1; 0 0 0 0 0; 0 0 0 7 9; 0 0 0 0 0; 0 0 0 0 0; 9 6 0 0 1; 1 1 1 0 0];

How can i make the sum of elements>3, under the condition that there are at least 3 zeros between the last element of one and the first element of the next sum?

Output should be: E=[9 32 16 19]

thanks!

[Azzi Abdelmalek]

How did you get this result?

[Image Analyst]

Next sum? Why is there more than one sum??? Looks like you need to read this before you fix your post.

Answer 1

[Azzi Abdelmalek]

a=[2 3 0 0 4; 0 0 0 0 0; 0 5 3 0 4; 14 4 0 1 1; 0 0 0 0 0; 0 0 0 7 9; 0 0 0 0 0; 0 0 0 0 0; 9 6 0 0 1; 1 1 1 0 0]
b=reshape(a',1,[]);
id=~b;
ii=strfind(id,[1 1 1 0])+2;
ii=[0 ii numel(b)];
for k=1:numel(ii)-1
  out(k)=sum(b(ii(k)+1:ii(k+1)));
end
out

[hdiba]

Thank you very much for your help! it works perfectly! is there any way to pick out the row in the matrix where a sum started? in our example: [1 3 6 9]

[Azzi Abdelmalek]

[~,idx]=ind2sub(size(a'),ii(1:end-1)+1)

[hdiba]

Now I want to work with larger matrix and have to extend the condition from 3 to 36 zeros between sums. I edited it with:

b=reshape(a',1,[]);
id=~b;
ii=strfind(id,[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0])+2;
ii=[0 ii numel(b)];
for k=1:numel(ii)-1
  out(k)=sum(b(ii(k)+1:ii(k+1)));
end
[~,idx]=ind2sub(size(NMatrix'),ii(1:end-1)+1);

it seems to work for the sums but not for the rows. can u please check the edited code? thanks

[Azzi Abdelmalek]

If you change the criterion 3 zeros to 36, you need to change the code

n=36
ii=strfind(id,[ones(1,n) 0])+n-1;

[hdiba]

Thanks! one last thing: is there any way to get the number of elements(inclusive zeros) in each sum? in the example above:

sum1=9 ->5 
sum2=32 ->9
sum3= 16 ->2
sum4=19 ->8

i would like to apply this for my large matrix with the condition of 36 zeros for sums. thanks!

[Image Analyst]

Yes, but first we need to know how you got those numbers. For example, assuming the sums are row sums, the first row is [2 3 0 0 4], which sums to 9. There are 2 regions, and 3 elements (2 (a 2 and a 3) in region 1 and 1 (a 4) in region 2). So how do you get a 5?

[hdiba]

the sum1=9 consists of 5 elements: 2+3+0+0+4. i count the zeros between the regions as elemnts as well. to be more precise, i am looking for the number of elements between first and last summand in a sum.

[Image Analyst]

Then you simply want the number of columns in the matrix:

[rows, columns] = size(yourMatrix);

In your example, columns will be 5.

[hdiba]

but the sums are not row sums. this was just an assumption you've done in the comment above.

[hdiba]

is there any way to get the number of elements in a sum? maybe somehow with the difference between the end position and beginning position of the sum? in our example for sum 9=2+3+0+0+4, there are 5 summands