vectorize a function that calls the itterator (condition in a loop)

Hello, I am trying to go through a matrix (x,y) and at each point of the matrix, if the number is in-between a certain number, add a 1 to the same zero matrix, else put a zero.

Here is my code in classical object programming:

if true

 sz = size(img);
 A = zeros(sz(1),sz(2));

 for i = 1:sz(1)
    for j = 1:sz(2)
        if (img(i,j) < minthreshold)||((img(i,j) > maxthreshold)))
            A(i,j) = 0;
        else
            A(i,j) = 1;
        end
    end
 end

I know how to go through a matrix with the vectored syntax, but I wouldn't know when that condition is respected, I want to reference the (i,j) where the matrix, at the time, iterating. I thought the loop could be replaced by:

if true
   if (img(1:1:sz(1),1:1:sz(2)) < minthreshold)||((img(1:1:sz(1),1:1:sz(2)) > maxthreshold))
          A() = 0;
      else
          A = 1;
      end
end

But when the condition is True, I don't know how to adress my matrix A() at the same location that the matrix img is at to put a value of 1 or 0.

Thank you!

Answer 1

[Stephen23]

Simplest:

A = img>=minthreshold & img<=maxthreshold

If you really wanted to, you could use indexing:

A = zeros(sz);
A(img>=minthreshold & img<=maxthreshold) = 1

[Marc-André Vigneault]

thank you very much :)

Answer 2

[Guillaume]

You don't use any if for that. You get the result as a logical array and use that logical array as a mask:

A = ones(size(img), 'like', img); 
isinrange= img < minthreshold | img > maxthreshold;  %note that you CANNOT use || here
A(isinrange) = 0;

However, since you're only putting 0 and 1 in your output, this can be simplfied even further to:

A  = ~(img < minthreshold | img > maxthreshold);
%or
A = img >= minthreshold & img <= maxthreshold;

Finally, note that

x(1:1:sz)

is exactly the same as

x(1:end)

and even simpler

x

as I have done above