MATLAB Tips

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General Programming Tips

  1. Compute the running time of a function all

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    tic; fft(rand(500)); disp( [’it takes ’ num2str(toc) ’s.’] );

  2. Locate the indice of minimum value in a matrice

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    [M,I]         = min(objMatrice(:)); % 'objMatrice' is the objective matrix
    [Irow,Icol]   = ind2sub(size(objMatrice),I);

  1. Sort ascending filenames based on number

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    sFile = dir([dir1 'temp*.mat']);
    %%% sort ascending filenames based on Number
    [~, reindex] = ...
           sort(str2double(regexp( {sFile.name}, '\d+', 'match', 'once' )));
    sFile        = sFile(reindex) ;

  2. Writing/Reading to a text file a list of 3-uplets.

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    % A is a matrix with 3 rows.
    fid = fopen(filename,’wt’);
    fprintf(fid, ’%f %f %f\n’, A);
    fclose(fid); % Retrieving the values back from file to matrix B.
    fid = fopen(filename,’r’);
    [B,cnt] = fscanf(fid,’%f %f %f’);

  3. Create a graphical waitbar

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    n = 100;
    h = waitbar(0,’Waiting ...’);
    for i=1:n
    waitbar(i/n);
    % here perform some stuff
    end
    close(h);

  4. Loading issue 

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    try
        load('xxx.mat') % x
    catch 
        datatemp = matfile('xxx.mat');  % x
        data     = datatemp.x;
    end

Sub-function Tricks

  1. Create a sub-function that takes optional arguments in a struct

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    function y = f(x,options)
    % parse the struct
    if nargin<2
    options.null = 0; % force creation of options
    end
    if isfield(options, ’a’)
    options.a = 1; % default value
    end
    a = options.a;
    if isfield(options, ’b’)
    options.b = 1; % default value
    end
    b = options.b;
    % Here the body of the function ...

    note: nargin returns the number of function input arguments given in the call to the currently executing function.

  2. Use varargin in function e.g. as following. A single function to generate two-dimensional (2D) line graphs, avoiding a long list of code for the generation of each graphic.

    PlotSet generates 2D plots, including multiple plots on a page. This code processes varargin as
    parameter pairs to set options. This makes it easy to expand the options. You can look for more information in the following book.

    Paluszek, M., and S. Thomas. MATLAB Machine Learning. Apress, 2016. https://books.google.com.au/books?id=jy75vQAACAAJ.

  3. Write a function fun(a,b,c) that can take an arbitrary number of arguments

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    function fun(args)
    default_values = {0.1246,1.2346,8.7643};
    args_present = cellfun(@isempty,args);
    default_values(args_present) = args(args_present);
    [a b c] = deal(default_values);

  4. Load a variable from a .mat file and then place that variable inside a structure with the same name

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    % Load the variable
    loadedData = load('myData.mat');  % This loads the data into a structure

    % Extract field names from the loaded data
    fieldNames = fieldnames(loadedData);

    % Loop through each variable and assign it to a new structure with the same name
    for k = 1:length(fieldNames)
        varName = fieldNames{k};
        dataStruct.(varName) = loadedData.(varName);
    end
    % Now dataStruct has fields corresponding to the variables loaded from the .mat file

Mathematical Tips

  1. Generate n points x sampled uniformly at random on a sphere.

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    % tensor product gaussian is isotropic
    x = randn(3,n);
    d = sqrt( x(1,:).ˆ2+x(2,:).ˆ2+x(2,:).ˆ2 );
    x(1,:) = x(1,:)./d;
    x(2,:) = x(2,:)./d;
    x(3,:) = x(3,:)./d;

  2. Keep only the n biggest coefficients of a signal x (set the others to 0).

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    [tmp,I] = sort(abs(x(:))); x( I(1:end-n) ) = 0;

Plotting

  1. Draw a 3D sphere.

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    p = 20; % precision
    t = 0:1/(p-1):1;
    [th,ph] = meshgrid( t*pi,t*2*pi );
    x = cos(th);
    y = sin(th).*cos(ph);
    z = sin(th).*sin(ph);
    surf(x,y,z, z.*0);
    % some pretty rendering options
    shading interp; lighting gouraud;
    camlight infinite; axis square; axis off;

  2. Edit legend

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    [hhLeg,labelhandles] = legend(ax(1),htext,'location','NorthEast'...
        ,'box','off','Interpreter','LaTex','FontSize',fS);
    % hhLeg.ItemTokenSize =[20 18];
    labelhandles(5).LineStyle = '-';
    labelhandles(4).XData = [0.24 0.37];
    labelhandles(5).XData = labelhandles(4).XData;
    labelhandles(4).YData = labelhandles(4).YData + 0.07;
    labelhandles(5).YData = labelhandles(4).YData - 0.14;
    labelhandles(5).Color = col2(1,:);

  3. Copy all properties for Axes

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    ax(2) = axes('Position',ax(1).Position ...
                           ,'OuterPosition',ax(1).OuterPosition ...
                           ,'InnerPosition',ax(1).InnerPosition ...
                           ,'ActivePositionProperty',ax(1).ActivePositionProperty...
                           ,'ALim',ax(1).ALim...
                           ,'ALimMode',ax(1).ALimMode...
                           ,'color','none'...
                           ,'xtick',[],'ytick',[],'ztick',[]...
                           ,'xcolor','none','ycolor','none','zcolor','none'...
                           ,'Projection','perspective'...
                           ,'CameraPosition',ax(1).CameraPosition ...
                           ,'CameraPositionMode',ax(1).CameraPositionMode...
                           ,'CameraTarget',ax(1).CameraTarget...
                           ,'CameraTargetMode',ax(1).CameraTargetMode...
                           ,'CameraUpVector',ax(1).CameraUpVector...
                           ,'CameraUpVectorMode',ax(1).CameraUpVectorMode...
                           ,'CameraViewAngle',ax(1).CameraViewAngle...
                           ,'CameraViewAngleMode',ax(1).CameraViewAngleMode...
                           ,'DataAspectRatio',ax(1).DataAspectRatio...
                           ,'DataAspectRatioMode',ax(1).DataAspectRatioMode...
                           );
                       
    %      copyaxes(ax(1),ax(2))

  4. set handle in a figure invisible 

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    set(findall(hFig,'Type','arrow'),'visible','off')
    set(findall(hFig,'Type','textbox'),'visible','off')
    set(findall(hFig,'Type','axes'),'visible','off')
    set(findall(hFig,'Type','surf'),'visible','off')
    set(findall(hFig,'Type','patch'),'visible','off')
    set(findall(hFig,'Type','Line'),'visible','off')
    set(findall(hFig,'Type','contour'),'visible','off')

  5. plot at a specific plane 

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    tt = hgtransform(ax(2)); % establish plane 
    % X-axis rotation matrix and Z-axis translation matrix
    Rz = makehgtform('translate',[0 y(end) 0],'xrotate',1/2*pi,'yrotate',-1/2*pi);
    set(tt,'Matrix',Rz);

  6. Two axes in one figure

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    ax(1) = axes('box','on');hold(ax(1),'on')
    ax(2) = axes('Position',ax(1).Position ...
                  ,'color','none'...
                  ,'yAxisLocation','right'...
                  ,'box','off'...
                  ,'xTick',[]...
                  ...,'ytickLabel',[]...
                  ,'ycolor',[0.5 0.5 0.5]...
                  );
    hold(ax(2),'on')

  7. Iso-contours 

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    [cContourMap,hContourMap] = contourf(gca,XXAB',YYAB',ZZAB');
    set(hContourMap,'linestyle','none')
    yclimColorbar = [0 1];
    ytickColorbar = 0:0.2:1;
    colLevelist   = 0:0.1:1;
    hContourMap.LevelList = colLevelist;
    set(gca,'clim',yclimColorbar)
    hColorbar    = colorbar(gca);
    titleindex    = 'title';
    set(get(hColorbar1,'title'),'string'...
           ,titleindex...
           ,'FontSize',11 ...
           ,'interpreter','LaTex'...
           ,'FontName','Times New Roman' ...
           )
    set(hColorbar1...
           ,'ylim',yclimColorbar...
           ...,'ylim',[0 4]...
           ,'ytick',ytickColorbar...
           ,'Location','southoutside'...
           ... ,'AxisLocation','out'...
           ,'Units','Normalized'...
           ...,'Position',[0.1 0.2 0.6 0.03] ...
           ,'FontSize',11 ...
           ,'FontName','Times New Roman' ...
           )

  8. Circular legend for contour lines

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    hFigPos = hFig.Position;
    xCentre = 0.47;
    yCentre = 0.18;
    coll1 = flipud(coll1);
    radius = 0.07;
    radii = linspace(0.01,radius,round(size(coll1,1)/2));
    for iR = 1:length(radii)
        annotation(hFig,'ellipse', [xCentre - radii(iR)/2, yCentre - radii(iR)*hFigPos(3)/hFigPos(4)/2 ...
                                 , radii(iR), radii(iR)*hFigPos(3)/hFigPos(4)], ...
            'Color', coll1(iR,:), 'LineWidth', 1);
    end

  9. Generate gif

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    % Video to GIF Synchronization Script
    % Created by: Yu Xia
    % Location: Melbourne, Australia
    % Date: 2024.08.09

    % Initialize video file and reader
    videoFile = 'videoName.mp4';
    videoObj = VideoReader(videoFile);

    % Set output filename
    outputFilename = 'synchronized_animation.gif';

    % Get total number of frames
    numFrames = videoObj.NumFrames;

    % Create figure and axes
    hFig = figure('Color', 'white', 'Units', 'normalized', 'Position', [0.1 0.1 0.8 0.8]);
    ax(1) = axes('Parent', hFig, 'Position', [0.05 0.1 0.4 0.4], 'Box', 'on', 'Color', 'white');
    ax(2) = axes('Parent', hFig, 'Position', [0.5 0.1 0.4 0.4], 'Box', 'on', 'Color', 'white');

    % Hold axes for plotting
    hold(ax(1), 'on');
    hold(ax(2), 'on');

    % Configure second axes
    set(ax(2), 'XLim', [-60 60], 'YLim', [-9 -4], 'TickLength', [0.02 0.02], ...
        'XTick', -60:20:60, 'YTick', -9:1:-4, 'Box', 'on', 'XTickLabelRotation', 0);

    % Set labels for second axes
    xlabel(ax(2), '$\alpha$ ($^\circ$)', 'Interpreter', 'LaTeX', 'FontSize', 12);
    ylabel(ax(2), '$E$ (V)', 'Interpreter', 'LaTeX', 'FontSize', 12);

    % Process video frames
    for iAlpha = 1:numFrames
        % Read video frame
        videoFrame = read(videoObj, iAlpha);
        currentTime = videoObj.CurrentTime;
        
        % Display video frame
        imshow(videoFrame, 'Parent', ax(1));
        
        % Plot data on second axes (replace 'xx' with actual data)
        plot(ax(2), xx, xx, 'k', 'MarkerSize', 4, 'Color', col2, 'LineWidth', 1.3, 'LineStyle', '-');
        
        % Capture frame and convert to image
        frame = getframe(hFig);
        im = frame2im(frame);
        
        % Write frame to GIF
        if iAlpha == 1
            [imind, cm] = rgb2ind(im, 256, 'nodither');
            imwrite(imind, cm, outputFilename, 'gif', 'LoopCount', inf, 'DelayTime', 0.1);
        else
            imind = rgb2ind(im, cm, 'nodither');
            imwrite(imind, cm, outputFilename, 'gif', 'WriteMode', 'append', 'DelayTime', 0.1);
        end
    end

    % Close figure
    close(hFig);

    disp('GIF creation complete.');

  10. Store section title into a tiff image

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function metaTiffEdit(printName, sectionName)
 
    if nargin < 2 || isempty(sectionName)
        % Automatically retrieve section title if sectionName is not provided
        sectionName = getSectionTitleFromActiveScript();
    end
 
    % Open the TIFF file for editing
    fileID = Tiff([printName '.tif'], 'r+');
    
    % Get the current script directory and file details
    [currentDir, Filename, ext] = fileparts(matlab.desktop.editor.getActiveFilename);
    fprintf('current working directory: %s\n', currentDir);
 
    % Prepare metadata string
    metaData = sprintf('%s%s%s', currentDir, Filename, ext);
    
    % Set the TIFF tags
    fileID.setTag('Artist', metaData);
    % fileID.setTag('Copyright', 'Your Copyright Info');
    % fileID.setTag('DateTime', datestr(now, 31));  % Using current date and time
    % fileID.setTag('DocumentName', 'Document Name');
    
    fileID.setTag("ImageDescription", sectionName);
    fileID.close;
end
 
function sectionTitle = getSectionTitleFromActiveScript()
    % Get the active editor object
    activeEditor = matlab.desktop.editor.getActive;
    
    % Get the position of the cursor
    cursorPosition = activeEditor.Selection(1);
    
    % Retrieve the content of the script as lines
%     lines = strsplit(activeEditor.Text, '\n');
    lines = splitlines(activeEditor.Text);
       
    % Initialize sectionTitle to an empty string
    sectionTitle = '';
    
    numLines = length(lines);
    cursorPosition = min(cursorPosition,numLines);
    
    
    % Find the most recent section title, starting from the current line
    for i = cursorPosition:-1:1
        if startsWith(strtrim(lines{i}), '%%') && ...
                ~startsWith(strtrim(lines{i}), '%%%')
            sectionTitle = strtrim(lines{i});
            break;
        end
    end
    
    % If no section title was found, default to 'Untitled Section'
    if isempty(sectionTitle)
        sectionTitle = 'Untitled Section';
    end
    
    % Optionally, remove the '%%' characters from the section title
    sectionTitle = strrep(sectionTitle, '%%', '');
end

Drawing Technique

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