MATLAB: Can I update a pie chart data in real time using XData and YData in MATLAB 7.12 (R2011a)

MATLAB

How can I update a pie chart in real time, similar to using 'XData' and 'YData' to update a plot in real time?

Best Answer

PIE does not produce a single handle for the entire plot; instead, it produces a collection of PATCH graphics to represent the slices, and a series of text labels. Updating the PIE would involve first, normalizing the data vector then creating cartesian coordinates from the polar representation of the data vector. Therefore, the most direct way to work around this issue is to call the PIE function repeatedly using the new data while maintaining the same axes.

This segment of code walks through the resulting workaround.

clc, clear all, close all;
a = rand(25,1); % original data vector "a"
pie(a);
hold on;        % plot subsequent data on same axes
b = rand(25,1); % new data vector "b"
clf('reset')    % clear current figure axes
pie(b)          % redraw PIE with new data vector b
drawnow;        % draw immediately and clear handle queue
hold off;       % henceforth, create new axes

Related Solutions

MATLAB: How to move and rescale a pie chart drawn over another graphic

The ability to move and rescale a pie chart is not available in MATLAB.

To work around the issue, move and rescale the patch graphics and text labels individually.

PIE does not produce a single handle for the entire plot; instead, it produces a collection of PATCH graphics to represent the slices, and a series of text labels. The most direct way to move the pie is to directly modify the position and size of the individual slices and labels. This segment of code walks through the resulting list, scaling and moving pie slices (represented as patch graphics) and text:

contour(membrane(1));
axis square;
hold on;
X = [1 3 5];
h = pie(X);
%Move to xpos,ypos and rescale by scale
xpos = 10;
ypos = 22;
scale = 5;
for k = 1:length(h) % Walk the vector of text and patch handles
      if strcmp(get(h(k),'Type'),'patch') % Patch graphics
          XData = get(h(k),'XData');  % Extract current data
          YData = get(h(k),'YData');
          set(h(k),'XData',XData*scale + xpos); % Insert modified data
          set(h(k),'YData',YData*scale + ypos);
      else    % Text labels
          Pos = get(h(k),'Position'); % Extract
          set(h(k),'Position',Pos*scale + [xpos ypos 0]); % Insert
          set(h(k),'FontSize',8);
      end
end

MATLAB: How can i change the colours of segmentation on a chart pie

Unforunately the pie() function does not allow you to directly specify the face color of each wedge as inputs.

Here are two ways to change the wedge colors after producing the pie plot.

Produce a demo pie chart & define colors

ax = gca(); 
pieData = [.3 .4 .3]; 
h = pie(ax, pieData); 
% Define 3 colors, one for each of the 3 wedges
newColors = [...
    1,       0.41016, 0.70313;   %hot pink
    0,       1,       0.49609;   %spring green
    0.59766, 0.19531, 0.79688];  %dark orchid

Option 1 : change the axes colormap

You can use on of Matlab's many pre-defined colormaps or you can create your own has we've done above. This works with pie() and pie3() objects.

% ax is the handle to the pie chart axes
% newColors is a nx3 matrix for n pie-wedges
ax.Colormap = newColors; 
% to use a pre-defined colormap (in this example, 'Spring')
% h is the output to pie()
ax.Colormap = spring(numel(h)/2);

Option 2: Change the FaceColor of the wedges

For pie() objects

% h=pie() output is a vector of alternating patch and text handles. 
% Isolate the patch handles
patchHand = findobj(h, 'Type', 'Patch'); 
% Set the color of all patches using the nx3 newColors matrix
set(patchHand, {'FaceColor'}, mat2cell(newColors, ones(size(newColors,1),1), 3))
% Or set the color of a single wedge
patchHand(2).FaceColor = 'r';

For pie3() objects

% Extract the surface and patch handles from the output to pie3()
surfaceHand = findobj(h, 'Type', 'Surface'); % edges
patchHand = findobj(h, 'Type', 'Patch');     % tops & bottoms
% Set the color all patches (tops & bottoms) and surfaces (edges) using the nx3 newColors matrix
set(surfaceHand, {'FaceColor'}, mat2cell(newColors, ones(size(newColors,1),1), 3));
set(patchHand, {'FaceColor'}, mat2cell(repelem(newColors,2,1), ones(size(newColors,1)*2,1), 3));

Best Answer

Related Solutions

MATLAB: How to move and rescale a pie chart drawn over another graphic

MATLAB: How can i change the colours of segmentation on a chart pie

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