# Plotting pie charts over GraphPlot

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Woda on 19 Oct 2021
Answered: Woda on 21 Oct 2021
Hi,
I want to plot pie-charts over the nodes of a graph plotted as a GraphPlot object such that the middle of the pie sits exactly at the node.
Hence, I want to do something like this
s = [1 1 1 1 2 2 3 4 4 5 6];
t = [2 3 4 5 3 6 6 5 7 7 7];
G = graph(s,t);
p = plot(G);
and then add an axes and plot a pie chart over one of the nodes with
axes('Position',[?, ?, pie_size, pie_size]);
X = [1 0.5 2.5 2]; pie_chart = pie(X, repmat({''},size(X)));
The ? represent the coordinates of the new plot inside the graph plot.
While I can read out the coordinates of the nodes in the graph plot from p.XData and p.YData, these seem to be relative to the center of the plot in units which are incompatible to any available unit system in the axes function.
Does anyone know of a way to accomplish what I want (possibly also in a different way)?

Chunru on 19 Oct 2021
Edited: Chunru on 21 Oct 2021
Here is the updated answer. We play with the properties of pie_chart this time.
clf
s = [1 1 1 1 2 2 3 4 4 5 6];
t = [2 3 4 5 3 6 6 5 7 7 7];
ax=axes;
G = graph(s,t);
p = plot(G);
hold on
X = [1 0.5 2.5 2];
pie_chart = pie(ax, X, repmat({''},size(X)));
% Align the pie_chart
idx = find(p.NodeLabel == "1");
xn=p.XData(idx);
yn=p.YData(idx);
scale = 0.2;
for k = 1:length(pie_chart)
if pie_chart(k).Type=="patch"
XData = pie_chart(k).XData;
YData = pie_chart(k).YData;
set(pie_chart(k),'XData', XData*scale + xn);
set(pie_chart(k),'YData', YData*scale + yn);
set(pie_chart(k),'FaceAlpha', 0.5);
else % Text labels
Pos = pie_chart(k).Position;
pie_chart(k).Position = Pos*scale + [xn yn 0];
end
end
axis equal % clf
% % Pie chart
% ax(1)=axes;
% X = [1 0.5 2.5 2]; pie_chart = pie(X, repmat({''},size(X)));
% set(findobj(pie_chart, 'Type', 'Patch'), 'FaceAlpha', 0.8)
%
% % Graph
% ax(2)=axes;
% ax(2).Position = ax(1).Position;
%
% s = [1 1 1 1 2 2 3 4 4 5 6];
% t = [2 3 4 5 3 6 6 5 7 7 7];
%
% G = graph(s,t);
% p = plot(G);
% ax(2).Color='none';
%
% % Align the graph
% idx = find(p.NodeLabel == "1");
% xn=p.XData(idx);
% yn=p.YData(idx);
%
% % scale the graph by 0.5 (adjust this number)
% p.XData = (p.XData-xn)*.5;
% p.YData = (p.YData-yn)*.5;
%
% ax(2).XLim = ax(1).XLim;
% ax(2).YLim = ax(1).YLim;
% s = [1 1 1 1 2 2 3 4 4 5 6];
% t = [2 3 4 5 3 6 6 5 7 7 7];
% ax(1) = axes;
% G = graph(s,t);
% p = plot(G);
% ax(2)=axes;
%
% ax(2).Color='none'
% X = [1 0.5 2.5 2]; pie_chart = pie(X, repmat({''},size(X)));
% set(findobj(pie_chart, 'Type', 'Patch'), 'FaceAlpha', 0.3)
Chunru on 21 Oct 2021
Updated.

Woda on 21 Oct 2021
Thank you very much for your patience - the last solution is spot on!