Selecting all pixels except one pixel

Say that we have a 3x3 matrix. If we type x(:), this will select all the elements in the matrix, right?

How can we select all the elecments except element x(2,2)? What should we type in this case?

Thanks.

[Image Analyst]

What are you doing? Because if you're doing something like linear filtering via convolution or morphological filtering, you would do this be proper selection of the kernel.

Answer 1

[Iain]

You need to use linear or logical indexing to do that. In this case, linear would be easier:

The indices for a 3x3 are:

[1 4 7;

2 5 8;

3 6 9];

So you can access it via x([1:(1 before the one you don't want) (1 after the one you don't want:end]), so for your example:

x([1:4 6:9]);

[Iain]

Logical indexing would use something more like x(x > 5), and it would select only those elements greater than 5.

[Iain]

I should also say that x .* (x>5) also "selects" the bits of x that are greater than 5, but it keeps the shape of x.