MATLAB: Set object property of a user-defined class

oopset object property user-defined class

Hello,

I want to set the properties "nb_pixel_horiz" and "nb_pixel_verti" of an object "p" that has the user-defined class "Picture".

I wrote

classdef Picture    
      properties
          nb_pixel_horiz;
          nb_pixel_verti;
      end    
      methods
      end    
end

And I want to write in the main command something like:

p = Picture;
set(p,'nb_pixel_horiz', 2000);
set(p,'nb_pixel_verti', 1000);

But it does not work. Could someone help me?

Thanks! Guillaume

Best Answer

Hey, Another Guillaume!

You need to derive from hgsetget, so:

classdef Picture < hgsetget
  properties
       nb_pixel_horiz;
       nb_pixel_verti;
  end    
end

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MATLAB: Editing superclass properties from subclasses

Why do you want different objects to share ( "synchronize" ) property values? However, without looking at the documentation you refer to.

    super = SuperClass;
    sub = SubClass;
    sub.handle.Description = 'Hello';
    super.handle.Description
    super.handle.Description = 'World';
    sub.handle.Description

returns

    ans =
    Hello
    ans =
    World

where

    classdef   SuperClass < handle
        properties
            handle = DescriptionContainer();
        end
    end

and

    classdef   DescriptionContainer < handle
        properties
            Description
        end
    end

and

    classdef    SubClass < SuperClass
        properties
            another_property
        end
    end

With the help of a dependent property together with set and get methods, I think it would be possible to hide (Access=protected) the property, which I call "handle".

The word, "Editing", in the subject line makes me unsure regarding your intent.

"Maybe: Another way ..." sounds strange to me. Wouldn't that overly complicate the dependencies.

"events and listeners" if nothing else it complicates the debugging.

MATLAB: Apply function with two variables

You should be able to make your code significantly faster by vectorizing it (see this article on vectorization) instead of using two for loops.

In your case, since you have two vector inputs x and y and you want to evaluate a 2D Gaussian function at each pair of points, you can use the meshgrid function to create a grid for you (see the documentation for more information) .

Using meshgrid, a vectorized form of your function might look like

function [ intensity_value ] = twoDimensionalGaussian( x, y, x_centre, y_centre, sigma_x, sigma_y, sigma_xy, amplitude, background)
% create a meshgrid for the normalized x and y values
[x_normalised, y_normalised] = meshgrid((x - x_centre)/sigma_x, (y - y_centre)/sigma_y);
% compute the Gaussian values
intensity_value = background + amplitude*exp(-(x_normalised.^2 + y_normalised.^2 + 2*sigma_xy/(sigma_x*sigma_y)*x_normalised.*y_normalised));
end

Notice in the code above that the * and ^ operators were replaced with the .* and .^ operators, which work element-wise (see the differences between the documentations of the .* operator and the * operator if the distinction is not clear).

Then instead of looping over the possible x and y values, you could call your function as

I = twoDimensionalGaussian(1:1280, 1:1024, x_centre, y_centre, sigma_x, sigma_y, amplitude, background);

If you have the Statistics Toolbox, you might also consider using the built-in mvnpdf function instead, which can be used to compute values of a 2D Gaussian function (see the documentation page for more information).

Best Answer

Related Solutions

MATLAB: Editing superclass properties from subclasses

MATLAB: Apply function with two variables

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