How to extract a matrix from the indexing data

Hi there,

I have a matrix A=[256*256]. Now i find all the pixels that have values greater than certain threshold using

[row, column, dataValues] = find(A > 5);

my row matrix is 11854*1 and my column matrix is also 11854*1.

Now how do i extract these rows and columns from A. I want to compare(see) two matrices(original and extracted) side by side so i want both matrices to be of same size as well. All the pixels not satsiying the condition be 0.

Thank you

[Walter Roberson]

Suppose that you had an L shape that was the full height of A but half the full width of A, and suppose it was against the bottom left. Now in that scenario, what would your desired output be?

Make it simple

 .++      .
 .++      . 
 .++++    .
 .++++    .

The periods are outside of the image showing the "frame".

What would you want out in this case?

Answer 1

[Fangjun Jiang]

They can not be scaled to the same size as A. Maybe you are looking for the matrix "index" in the below example?

see help of ind2sub() or sub2ind()

B=rand(5);
index=B>0.5;
[row, column, dataValues] = find(index)

[Fangjun Jiang]

All the pixels not satsiying the condition be 0.

index=A>5;
B=A;
B(~index)=0