Manually adding plots and legends with a Button Press

I have a button call back that I want to plot a set of data in a particular colour and add the legend. I then want to be able to press the button and each time a different data set is plotted in a different colour and its legend text to match the colour.

I First count the number of times the button has been pressed (its initially set to 1)

nplts=getappdata(0,'NominalPlotcount')

%Then I define the colour of my plot depending on this value.

nplts=getappdata(0,'NominalPlotcount')
 switch nplts
     case 1    
     colour='r'
     case 2
     colour='b'   
     case 3
     colour='g'  
     case 4
     colour='k'  
     otherwise
     colour='r'
 end    

 I then perform the plot and increment my plot counter nplts, and add the legend.

   plot(x,N(:,1),colour,'MarkerSize', 4, 'Marker','o','LineWidth',1)    
   legText=get(handles.editLegend,'String');
   legend(legText)
   setappdata(0,'NominalPlotcount',nplts+1);

My legend doesn't concatenate to whats already there. I have tried

     txt1=get(legend(gca),'String');
     txt1=[txt1,legText];
     hleg=legend(txt1);

But this just adds all the legend items in a single colour. Im really stuck now, any suggestions please?

Thanks Jason

[Jason]

I've read something about

legend('-DynamicLegend');

(<http://undocumentedmatlab.com/blog/legend-semi-documented-feature>)

But not sure how it works

Answer 1

[Ingrid]

if I understand your question correctly this should work, since you need to be placing brackets around each legend entry for matlab to interpret it is separate entries and hence assign a different colour

       txt1=get(legend(gca),'String');
       txt1=['''' txt1 '''' ',' '''' legText '''']
       eval(['hleg=legend(' txt1 ')']);

[Jason]

Thanks for your reply. But Im getting this error:

Undefined function 'eval' for input arguments of type 'cell'.

Also why so many ' in the:

txt1=['''' txt1 '''' ',' '''' legText '''']

[Ingrid]

because ' is required to define a string so you need two ' to define an apostrophe in a string and you need one apostrophe before and one after to define that it is a string (I know, complicated, but that's the way to work with strings in Matlab)

the error of cell type is probably because you get txt1 from the current legend. I think it is better if you store the txt1 each time in the handles structure so that you can use the correct format

so

txt1 = handles.txt1; % for this you first need to initialize an empty txt1 in the OpeningFcn of your gui
txt1=['''' txt1 '''' ',' '''' legText ''''];
eval(['hleg=legend(' txt1 ')']);
handles.txt1 = txt1;
% Update handles structure
guidata(hObject, handles);

[Jason]

Hi. Im still getting the same error:

Heres my code:

       legText=get(handles.editLegend,'String')  %get new legend text
       txt1=get(legend(gca),'String');           %get current legend items
       txt1=['''' txt1 '''' ',' '''' legText ''''];
       eval(['hleg=legend(' txt1 ')']);Text
       handles.txt1 = txt1;
       % Update handles structure
       guidata(hObject, handles);

In my openingFCN I have:

%To allow legend to manually change text colours
handles.txt1 = '';

% Update handles structure
guidata(hObject, handles);

[Ingrid]

you are still getting the current legend for txt1 (second line in your code) instead of using

txt1 = handles.tx1;

to set the value of txt1;

also it is not clear how you obtain the legText, is this from an editText field or is it a user defined field?

[Jason]

Hi, its from an edittext field

I now have my code as: legText=get(handles.editLegend,'String')

      %txt1=get(legend(gca),'String');
       txt1 = handles.tx1;
       txt1=['''' txt1 '''' ',' '''' legText '''']
       eval(['hleg=legend(' txt1 ')']);Text
       handles.txt1 = txt1;
       % Update handles structure
       guidata(hObject, handles);

and get: Reference to non-existent field 'tx1'.

Error in ZemaxDistortion>pushbuttonTol_Callback (line 661)
     txt1 = handles.tx1;

[Jason]

Ha, I see a typo here

   txt1 = handles.tx1;

OK so I've sort of got it working but its still not right. I have added 2 graphs, names plot 1 and plot 2. But the legend reads

i.e. there is a data 1, data 2 and data 3 from somewhere?. Also the first legend item isn't plot 1.

Answer 2

[Joseph Cheng]

why not try something like this out

clc; clear all;
nplts = 0;
legendstr = [];
figure(1),hold on;
cont = input('plot another rand plot?: ','s');
while ~isempty(cont)
    nplts = nplts+1;
     switch mod(nplts,5)
         case 1    
            colour='r'
         case 2
             colour='b'   
         case 3
            colour='g'  
         case 4
            colour='k'  
         otherwise
            colour='r'
     end     
     plot(randi(1000,1,100),colour),legend('show');
     hlegend =  findobj(gcf,'Type','axes','Tag','legend');
     legendstr = [legendstr;['another plot ' num2str(nplts)]];
%      legendstr =get(legend(gca),'String');
     legend(legendstr)
     cont = input('plot another rand plot?: ','s');
end

[Jason]

Thansk for this. I actually want the text thats entered in an edit box to be added.

I get the text from the edit box:

legText=get(handles.editLegend,'String')

and then when I change your concatenation line to

legendstr = [legendstr;[legText]];

I get the error

Error using vertcat
Dimensions of matrices being concatenated are not consistent.

[Joseph Cheng]

well you would then convert what you want into a cell array which is a few edits to the example code of:

legendstr = {}; %note the { brackets
%and then down below
legendstr(nplts) = %user input text;