ezimage.m

function ezimage(fun)
% Please report bugs and inquiries to:
%
% Name   : Rody P.S. Oldenhuis
% E-mail : oldenhuis@gmail.com
% Licence: 2-clause BSD (See Licence.txt)

% If you find this work useful, please consider a donation:
% https://www.paypal.me/RodyO/3.5

% If you want to cite this work in an academic paper, please use
% the following template:
%
% Rody Oldenhuis, orcid.org/0000-0002-3162-3660. "testfunctions" <version>,
% <date you last used it>. MATLAB Test functions for global optimization
% algorithms. https://nl.mathworks.com/matlabcentral/fileexchange/23147-testfunctions

    % make sure the path is OK
    prevpath = path;
    path(path, genpath(fileparts(mfilename('fullpath'))));

    % Path must be reset, even if something fails;
    % use TRY-CATCH to accomplish this
    % TODO: use onCleanup? -> incompatible with older MATLAB...
    try

        % EZIMAGE() takes no input, or a function handle
        if (nargin == 0)

            % available functions
            functions = dir([fileparts(mfilename('fullpath')) filesep 'single-objective-unconstrained']);
            functions = cellfun(@(x) x(1:end-2), {functions.name}, 'uniformoutput', false);
            functions = functions(3:end);

            % show list
            clc
            fprintf(1, 'Single-objective functions:\n');
            for ii = 1:numel(functions)
                fprintf(1, ['[', num2str(ii), '] ', functions{ii}, '\n']);
            end
            fprintf(1, '\n');

            % select one
            while true
                num = str2double(input('Type the number of the function you wish to plot: ', 's'));
                if isfinite(num) && (num <= numel(functions)), break, end
            end

            % set proper function
            evalc(['fun = @', functions{num}]);

        else
            if ~isa(fun, 'function_handle')
                path(prevpath);
                error('ezimage:no_function', ...
                    'Please provide a function handle to the function to plot.');
            end
        end

        % evaluate function with no argument to get some
        % info about the function
        [dims, lb, ub, solution, minimum] = feval(fun);

        % if the number of dimensions exceeds 3, we can't plot
        if (dims > 2) || ~isfinite(dims) % [inf] means arbitrary # dimensions
            path(prevpath);
            error('ezimage:too_many_dimensions',...
                'Given function requires %d dimensions to be plotted, and we live in a 3-D world.', dims+1);
        end

        % initialize
        x1 = linspace(lb(1), ub(1), 150);
        x2 = linspace(lb(2), ub(2), 150);
        x3 = zeros(length(x1), length(x2));

        % simply loop through the function (most functions expect
        % [N x 2] vectors as input, so meshgrid does not work)
        for ii = 1:length(x1)
            for jj = 1:length(x2)
                x3(ii, jj) = fun([x1(ii), x2(jj)]);
            end
        end

        % build simple grid for axes
        [x1, x2] = meshgrid(x1, x2);

        % draw surface
        figure, hold on
        surf(x1', x2', x3, 'Linestyle', 'none')

        % draw minima
        if ~isnan(solution)
            plot3(solution(:,1), solution(:,2), repmat(minimum, size(solution,1), 1), ...
                'r.', 'MarkerSize', 20);
        end

        % tiles, labels, legend
        xlabel('x_1'), ylabel('x_2'), zlabel('F(x_1, x_2)')
        if (size(solution,1) > 1)
            legend([func2str(fun), '-function'], 'Global Minima')
        else
            legend([func2str(fun), '-function'], 'Global Minimum')
        end

        % finalize
        view(-40, 30)
        set(gcf, 'renderer', 'openGl');

    % something's wrong
    catch ME
        path(prevpath);
        rethrow(ME);
    end

    % reset previous path
    path(prevpath);

end