looping thru multiple line data in UIAxes plot and writing all X,Y data to an array

Hello, i have a set of line plots on a UIAxes on a UIFigure using Appdesigner.

Note each plot has differing X coordinates

I want a way to be able to save all these plots so that I can revisit later and add further plots to it.

The approach I was going to take was to access the line objects and loop through assigning each X,Y datat set to a data array that I could save out and then recal at a later date.

     ax=app.UIAxes; 
     L=ax.XLim;
     L2=L(2);                          % Get max number on x-axis
     h1 = findall(ax, 'type', 'line')  % Get just line objects for now 
     n=numel(h1);                      % Number of line plots (will do text objectes later)
     H=nan(L2,2*n)                     % Create an array of Nans to hold all data   (row,cols)    
                                       % Each line requires its X data to be saved also             

Now loop thru' all line items and splat the X,Y data to the array

     for(i=1:n)
         t = h1(i)    
         H(:,(2*i)-1)=(t.XData)';
         H(:,2*i)=(t.YData)';    
     end    
     H

But Im getting the following error

     Unable to perform assignment because the size of the left side is 120-by-1 and the size of the right side is 100-by-1.
     
     Error in GenericDataAnalysis/ReadHeadersButtonPushed (line 533)
     H(:,(2*i)-1)=(t.XData)';

I suspect its to do with non-equal length of data sets. Perhaps I need some sort of padding for the missing data?

This is my current output:

     L2 =     
     120
     
     h1 =      
     7×1 Line array:
     
     Line    (20s Delay)
     Line    (15s Delay)
     Line    (9s Delay)
     Line    (5s Delay)
     Line    (2s Delay)
     Line    (FC Top)
     Line    (FC Btm)
     

The second part of my question, is whats the best approach to retain the colours and text objects?

Remember, i don't just want the graphic saved, I want to be able to add data to it later from within my GUI.

Thanks

Jason

Answer 1

[Rik]

I would suggest a struct array. That way you can store all relevant properties and you can fairly easy recreate the line objects.

[Jason]

Hi Rik, that is an awesome idea - thanks.

After trying the following: (I see its possible to assign "objects" to a struct field so I've assumed I dont need to loop thru each line plot object, I can just save them "collectively" and just loop thru them once I load them back to give me my plots - is this true?

    ax=app.UIAxes;
    ax.Children;
    h1 = findall(ax, 'type', 'line')      % Line objects
    nlines=numel(h1);
    h2 = findall(ax, 'type', 'text')      % Text objects
    ntext=numel(h1);
    datastruct.nlines=nlines;
    datastruct.ntext=ntext;
    datastruct.Lines=h1;                  % Can assign objects, so assign the h1
    datastruct.Text=h2;
    leg=ax.Legend

% Save as a Mat file
    try
         [file,folder]=uiputfile({'*.mat','Matlab Files'},'Save Data',app.startfolder);
    catch
        [file,folder]=uiputfile({'*.mat','Matlab Files'},'Save Data','C:\');
    end    
    app.startfolder=folder;
    savepath=fullfile(folder,file)
    save(savepath,"-struct","datastruct")

But its failing to save correctly.

    Warning: Unable to save App Designer app object. Save not supported for matlab.apps.AppBase objects. 

When I try to load it back:

     [file,path,idx]=uigetfile({'*.mat'},'Load Mat (Matlab) File',app.startfolder); 
     path1=fullfile(path,file)
     variableInfo = who('-file', path1)           
     s=load(path1);  

    path1 =
    
    'C:\MATLAB_FILES\APPDESIGNER\GenericDataAnalysis\Data02.mat'
    
    Error using who
    Could not open C:\MATLAB_FILES\APPDESIGNER\GenericDataAnalysis\Data02.mat as a valid MAT-file.
    
    Error in GenericDataAnalysis/LoadPlotMatButtonPushed (line 625)
    variableInfo = who('-file', path1)

[Rik]

You're fairly close, but the errors are why I suggested using a struct array instead of an object array. Each object contains information about the parent object as well. that means you can only save and restore your current objectes, which isn't the goal.

By using a struct you can store all the properties you need to reconstruct the objects from scratch.

Don't be afraid of a for loop, they are very fast in Matlab.

[Jason]

Hi, when I tried this, I created a field in the Struct where I assign the complete line objects to the struct.

But then when I tried to save this out in a mat file, it complained it couldnt save the objects.

h1 = findall(ax, 'type', 'line')      % Line objects
datastruct.Lines=h1;

thats why I switched to usign "variables" instead