function plotHeatmap(results_all, x_values, y_values, fieldName, varargin)
%% plotHeatmap: Plots a heatmap for a field in a struct array.
%
% Usage:
% plotHeatmap(results_all, x_values, y_values, fieldName, ...
%       'FigNum', 1, 'Colormap', parula, 'CLim', [0 1], ...
%       'XLabel', '\alpha (degrees)', 'YLabel', 'BField (G)', ...
%       'Title', 'My Title', 'SaveFileName', 'heatmap.fig', ...
%       'SaveDirectory', 'results', 'SkipSaveFigures', false);

    % --- Parse optional inputs ---
    p = inputParser;
    addParameter(p, 'FigNum', []);
    addParameter(p, 'Colormap', parula);
    addParameter(p, 'CLim', []);
    addParameter(p, 'XLabel', '\alpha (degrees)');
    addParameter(p, 'YLabel', 'BField (G)');
    addParameter(p, 'Title', fieldName);
    addParameter(p, 'FontName', 'Arial');
    addParameter(p, 'FontSize', 14);
    addParameter(p, 'SkipSaveFigures', false, @islogical);
    addParameter(p, 'SaveFileName', 'heatmap.fig', @ischar);
    addParameter(p, 'SaveDirectory', pwd, @ischar);
    parse(p, varargin{:});
    opts = p.Results;

    N_y = length(results_all);
    N_x = length(x_values);

    % --- Preallocate data matrix ---
    data_matrix = NaN(N_y, N_x);
    for i = 1:N_y
        if isfield(results_all(i), fieldName)
            data_matrix(i, :) = results_all(i).(fieldName);
        else
            warning('Field "%s" does not exist in results_all(%d). Filling with NaN.', fieldName, i);
        end
    end

    % --- Create figure ---
    if isempty(opts.FigNum)
        fig = figure;
    else
        fig = figure(opts.FigNum);
    end
    clf(fig);
    set(fig, 'Color', 'w', 'Position', [50 50 950 750]);

    % --- Plot heatmap ---
    imagesc(x_values, y_values, data_matrix);
    colormap(opts.Colormap);
    if ~isempty(opts.CLim)
        caxis(opts.CLim);
    end
    set(gca, 'FontName', opts.FontName, 'FontSize', opts.FontSize, 'YDir', 'normal');

    % --- Labels and title ---
    xlabel(opts.XLabel, 'Interpreter', 'tex', 'FontName', opts.FontName, 'FontSize', opts.FontSize);
    ylabel(opts.YLabel, 'Interpreter', 'tex', 'FontName', opts.FontName, 'FontSize', opts.FontSize);
    title(opts.Title, 'Interpreter', 'latex', 'FontSize', opts.FontSize + 2, 'FontWeight', 'bold');
    colorbar;

    % --- Save figure ---
    Plotter.saveFigure(fig, ...
        'SaveFileName', opts.SaveFileName, ...
        'SaveDirectory', opts.SaveDirectory, ...
        'SkipSaveFigures', opts.SkipSaveFigures);

end