Plot graph with large dataset

Question

lucksBi 2017-5-23

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https://ww2.mathworks.cn/matlabcentral/answers/341602-plot-graph-with-large-dataset

评论： Asyran Abdullah 2018-8-30

Hi i want to know what does this type of graph mean? I got this while Using same code which works fine on small data but with large data it plots this graph.

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Answer 1

Steven Lord 2017-5-23

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https://ww2.mathworks.cn/matlabcentral/answers/341602-plot-graph-with-large-dataset#answer_268130

It means that your directed graph (stored as a digraph object) contains multiple connected components. You can see a smaller, simpler example on the documentation page for the conncomp function.

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Steven Lord 2017-5-24

编辑：Steven Lord 2017-5-24

在 MATLAB Online 中打开

By "simple graph" do you mean a connected graph? There's no function to do this automatically as far as I remember but yes, you can do this. Start adding edges between two nodes that are in different connected components; each time you do, you reduce the number of components by 1. Continue until everything is in one component.

Note that there are many different ways to do this; using the example with numbered nodes on the Wikipedia page to which I linked (which is an undirected graph, not a directed graph, but the same principles apply), you could connect the node with degree 0 to any (or many, or all) of the other nodes. If you connected it to the node with degree 1, for example, you'd get something like:

% Make the graph object
s = [1 2 3 4 5 6 7 4];
t = [2 3 4 5 6 7 3 6];
G = graph(s, t);
% Generate coordinates to make it look
% something like the Wikipedia diagram
x = [0 0 1 3 5 4 2];
y = [0 2 1 2 2 1 0];
h = plot(G, 'XData', x, 'YData', y);
% Highlight the previously isolated node in red
highlight(h, 1, 'NodeColor', 'r', 'MarkerSize', 8)
% Highlight the node to which I connected it in black
highlight(h, 2, 'NodeColor', 'k', 'MarkerSize', 8)

While I connected the red highlighted node to the black highlighted node for this example, I could just as easily have connected it to any other node, like:

% Remove edge (1, 2) and add edge (1, 3)
G = rmedge(G, 1, 2);
G = addedge(G, 1, 3);
figure
h = plot(G, 'XData', x, 'YData', y);
% Highlight the previously isolated node in red
highlight(h, 1, 'NodeColor', 'r', 'MarkerSize', 8)
% Highlight the node to which I connected it in black
highlight(h, 3, 'NodeColor', 'k', 'MarkerSize', 8)

Or if you wanted you could have both connections.

G = addedge(G, 1, 2);
figure
h = plot(G, 'XData', x, 'YData', y);
highlight(h, 1, 'NodeColor', 'r', 'MarkerSize', 8);
highlight(h, [2 3], 'NodeColor', 'k', 'MarkerSize', 8)