How do you use ./ operator on array of custom class

Hi,

I've written a custom class with overloads for mathematical operators. I now have arrays a and b and I want to do element-wise division.

My first guess was that the ./ operator would map the / operator over the elements of the array, however with mrdivide defined I get the error "Undefined operator './' for input arguments of type".

When I add the following code to my class

        function r = rdivide(a, b)
            for i = 1:length(a)
                r(i) = a / b
            end
        end

I get the error "Error using / Too many input arguments" with line numbers pointing into my mrdivide function. My mrdivide function seems to work when I use it on its own.

Is this the correct way to implement element-wise division?

Thanks.

[darova]

Did you try

[Rik]

@Darova that looks like an answer to me. When moving it to the answer section, could you make it code instead of an image?

I also have a suggestion for the code itself: use numel instead of length. That way this overload will also work for non-vector shaped arrays.

[Jefferson Carpenter]

Thanks matlab experts, that was the problem. Will use numel.

Answer 1

[darova]

[darova]

Remember about preallocation for faster execution

r = 0*a;
% r = zeros(size(a));

[Jefferson Carpenter]

Neither of those works here, r = 0*a calls into my overloaded mtimes operator and doesn't create an array of 0's, and if I write r = zeros(numel(a)) then inside my for loop I get a "Conversion to double is not possible" error since I'm ultimately filling the array with instances of my class, not with doubles.

[darova]

Hm, im not that good in MATLAB

Maybe someone of experts can suggests something

But one thing i suggest is defintely preallocation

[Rik]

Preallocation is a lot less important when dealing with an array of objects than it is with arrays of native Matlab data types. In this case r=a; could be enough (since you will be overwriting the entries anyway).

[Steven Lord]

If you want functions like zeros, ones, etc. to be able to create arrays of your objects filled with the equivalent of 0 or 1 in your class, see this documentation page.