用条件求矩阵的最小数组

Question

I want to find the minimum of a matrix say A . I could do it in this way:

NM = find(A==min(A));

but I need the minimum array of A which for it, c(NM) is not zero. How can I put this condition on finding minimum value?

Example:

c=[0,18,9,0,100,0]; 
A=[1,189,125,25,7,1];

I expext it returns 5.

Answer 1

You can use logical indexing to find the desired elements.

find(A==min(A(c~=0)))

Explanation:

Using logical indexing you first find indices of elements of c that are nonzero.

idx1 = c~=0;

then elements of A that correspond to indices of nonzeros elemets of c are extracted.

A1 = A(idx1);

then we find minimum of the extracted elements:

mn = min(A1);

again we use logical indexing to find elements of A that are equal to its minimum.

idx2 = A == mn;

finally using find the logical index idx2 converted to linear index.

result = find (idx2);

Answer 2

First convert your Matrix to a vector (otherwise the minimum of a Matrix is confusing, it might mean the minimum of each column).

Then you can sort the Vector and get the indexes

[val idx] = sort(A(:));

You can then use the indexes to sort your vector c

c = c(idx);

And finally get the first non-zero element of c:

c = c(c~=0);    
result = c(1);