gca when using subplots

Hi.

I have created a barchart on a figure and wanting to change the number of bins by adding a popupmenu to the figure. I assign the callback to this a function called setBins.

% Create pop-up menu on figure
 popup = uicontrol('Style', 'popup',...
           'String', {'5','10','20','50','100','200','500','1000','2000'},...
           'Position', [10 0 80 30],...
           'Callback', @setBins);    

   function setBins(source,event)
          fig = gcf;
          ax = fig.CurrentAxes;
          cla(ax)

          val = source.Value
          indx = source.String
          nbins=(indx(val,1))
          nbins=str2double(nbins)
          data=getappdata(0,'data');           %Data has already been saved using setappdata     
          [counts,xb]=hist(data(:,3),nbins);   %IMHIST ONLY HANDLES 8 & 16 BIT IMAGES, NOT 12BIT  

          bar(log10(xb),counts,'b','EdgeColor','b');  %Replot with user defined number of bins
          grid on;
          hold on
          xlim([min(log10(xb)) max(log10(xb))])        
          xlabel('log(Intensity)')
          ylabel('Frequency')
          set(gca,'fontsize',8)
          hold off

My question is, this works fine with one plot on the figure. If however, this figure has two subplots and this is subplot(1,2,1), how would I get the above code just to apply to this subplot?

Thanks Jason

Answer 1

[Adam]

The subplot call includes a return argument which is the axes handle for that subplot. I would advise to always use this form and keep the axes handles in an array so that you can then do what you wish to them in future either all together or individually from the array.

Relying on gca or equivalent methods as to what happens to currently be in focus is always liable to lead to some seemingly strange bugs (strange at least until you become familiar with the cause and its effect)

[Jason]

so use:

ax1=subplot(1,2,1)
ax2=subplot(1,2,2)

but how do I then call this in the setBins function ?

[Adam]

'Callback', @(src,evt) setBins( src, evt, ax1 )

Then your function signature will be:

function setBins(source,event,ax)

and get rid of:

fig = gcf;
ax = fig.CurrentAxes;

[Jason]

Thanks Adam

Answer 2

[Steven Lord]

Consider using the histogram function instead of hist. Once you've created a histogram plot, click the arrow icon on the figure toolbar then right-click on the histogram. Assuming you're using a numeric histogram rather than a categorical histogram, you will be able to select the "More bins" and "Fewer bins" options from the context menu that appears.

x = randn(10000, 1);
h = histogram(x);
plotedit on
% Now right-click on the histogram

You can also directly change the bin related properties of the histogram using the handle h if you want finer control over the number and location of the bins.

% Change the histogram to have only a few bins with narrower center bins
h.BinEdges = [-4 -2 -1 -0.5 0 0.5 1 2 4]

% Set the number of bins and let histogram choose their locations
h.NumBins = 11

[Sean de Wolski]

Very cool!