MATLAB Examples

Add Node Properties to Graph Plot Data Cursor

This example shows how to customize the GraphPlot data cursor to display extra node properties of a graph.


Create GraphPlot object

Create a GraphPlot graphics object for a random directed graph. Add an extra node property wifi to the graph.

G = digraph(sprandn(20, 20, 0.05));
G.Nodes.wifi = randi([0 1], 20, 1) == 1;
h = plot(G);

Enable Data Cursor Mode

Enable data cursor mode by selecting the data cursor icon in the figure toolbar.

Alternatively, you can select the Data Cursor item in the Tools menu, or type: datacursormode on.

With data cursor mode enabled, click a node in the graph to bring up the cursor display. The data cursor allows you to select nodes in a graph plot and view properties of the nodes. By default, the data cursor for an undirected graph displays the node ID number and degree. For directed graphs, the display includes the node ID number, in-degree, and out-degree.

To display extra node properties, such as wifi, the data cursor callback function needs to be modified. For general information on using and customizing data cursors, see docid:creating_plots.f4-44221.

Customize Text Displayed by Data Cursor

Customize the text displayed by the data cursor by writing a new data cursor callback function.

1. Save the function GraphCursorCallback.m in your current directory:

function output_txt = GraphCursorCallback(obj,event_obj,NodeProperties)
% Display the position of the data cursor
% obj          Currently not used (empty)
% event_obj    Handle to event object
% output_txt   Data cursor text (character vector or cell array of character vectors).

h = get(event_obj,'Target');
pos = get(event_obj,'Position');
ind = find(h.XData == pos(1) & h.YData == pos(2), 1);

output_txt = {['Node ' num2str(ind)], ...
    ['Wifi: ' num2str(NodeProperties.wifi(ind))]};

A standard data cursor callback function accepts two input arguments. GraphCursorCallback accepts an additional input argument, NodeProperties, so that the data cursor gains access to the extra node properties in the graph, such as wifi.

2. Connect the GraphCursorCallback function to the data cursor by changing the UpdateFcn property of the data cursor manager object. This command uses an anonymous function to pass the G.Nodes table as the third input to GraphCursorCallback. This technique only takes a snapshot of the G.Nodes table, so if the graph properties subsequently change, then you need to change the UpdateFcn property again.

  hdt = datacursormode;
  hdt.UpdateFcn = @(obj,event_obj) GraphCursorCallback(obj,event_obj,G.Nodes);

3. Now that GraphCursorCallback is connected to the data cursor, delete any old data tips in the plot, then reenable data cursor mode and select a node. The new display of the data cursor includes the wifi node property as defined in GraphCursorCallback.