Can I plot a digraph on a geomap?

Hey there!

Similar to the question asked here (https://www.mathworks.com/matlabcentral/answers/472642-undirected-graph-network-with-latitude-and-longitude-as-node), I want to know if there is a way I could apply a digraph on geomap.

I couldn't find a way to create nodes with coordinate data (lat & lon), and thus gave arbitary ids (1,2,3...) for the nodes instead. After creating an array of targets (with similar id information), I make an arbitary array of weights and then plot it the graph.

 G = digraph(s,t,w,);
 plot(G, 'XData',x,'YData',y)
 

Because the problem is originally a geo problem, my x and y data is in the form of coordinates. However, is there a way to connect this information to GeoAxes so that I can tell Matlab to "accurately" overlay the digraph over the geomap?

A (probably messy) of doing it is to use an image as a background - which (I'm guessing) won't be reliable when reszing the plot.

--

PS: I've read the blog post (https://www.mathworks.com/matlabcentral/answers/472642-undirected-graph-network-with-latitude-and-longitude-as-node), while helpful for sure, Loren uses polygons to create the map of the US, which is overkill for what I want to achieve.

PPS: If you need some more info, please let me know in case I must've missed out anything.

[Michael Wish]

I wish someone would answer this! I need the exact same thing!

[Christofer Pankratz]

+1

while it's not an ideal solution, but could work for your purpose as well

https://de.mathworks.com/help/map/create-common-plots-over-basemap-images.html

Answer 1

[Avni Agrawal]

Hi @Trevor John D Silva,

I understand that you are trying to plot a diagraph on a geomap. Yes, you can overlay a directed graph (`digraph`) on a geographic map (`geoaxes`) in MATLAB. To do this, you would use the latitude and longitude as the `XData` and `YData` properties when plotting the graph. However, since `geoaxes` is for geographic plotting, you actually need to use the latitude for `YData` and longitude for `XData` because latitude corresponds to the Y-axis (north-south) and longitude corresponds to the X-axis (east-west) on a map.

Here is how you can create a `digraph` and plot it on a geographic map:

% Define the node IDs and their corresponding latitude and longitude
nodeIDs = [1, 2, 3, ...]; % Replace with your node IDs
    lats = [lat1, lat2, lat3, ...]; % Replace with your node latitudes
    lons = [lon1, lon2, lon3, ...]; % Replace with your node longitudes
    
    % Define the edges between nodes as source and target pairs
    s = [sourceNodeIDs]; % Replace with your source node IDs
    t = [targetNodeIDs]; % Replace with your target node IDs
    
    % Define the weights for the edges
    w = [weights]; % Replace with your edge weights
    
    % Create the directed graph
    G = digraph(s, t, w);
    
    % Create a geographic axes object
    figure;
    geoAx = geoaxes;
    
    % Plot the graph on the geographic axes
    % Note: The 'XData' and 'YData' inputs to 'plot' should correspond to longitude and latitude
    hold(geoAx, 'on'); % Hold on to plot multiple items on the geoaxes
    plot(geoAx, G, 'XData', lons(G.Edges.EndNodes), 'YData', lats(G.Edges.EndNodes), 'LineWidth', 2);
    
    % Optionally, you can customize the display, such as setting limits or adding a basemap
    geobasemap(geoAx, 'streets'); % Set the basemap to 'streets'
    geolimits(geoAx, [min(lats) max(lats)], [min(lons) max(lons)]); % Set geographic limits
    
    % Release the hold on the geoaxes
    hold(geoAx, 'off');

Make sure to replace `lat1`, `lat2`, `lat3`, `lon1`, `lon2`, `lon3`, `sourceNodeIDs`, `targetNodeIDs`, and `weights` with the actual values you have for your nodes and edges.

By using `geoaxes` and `geobasemap`, you can take advantage of MATLAB's built-in geographic plotting capabilities, which will handle things like map projection and resizing automatically. This approach will give you a more accurate and interactive map icompared to using a static image as a background.

I hope this helps!

[Francesco]

Hi @Avni Agrawal,

Thanks for your answer.

I have a problem plotting the digraph on geoaxes. When I run the plot row, It return me an error like this:

Error using plot

Data must be numeric, datetime, duration or an array convertible to double.

Error in congestion_research (line 140)

H = plot(geoAx,G,'XData',xdata,'YData',ydata,'LineWidth',LWidths);

In my case, geoAx is simply geoAx = geoaxes; G is a digraph, xdata and ydata are duble vectors with Cartesian Longitudes and Latitudes for each nodes and also LWidths is a double.

Where can I search for the error?

Thanks in advance

Francesco

[Chris Hooper]

I am also having this same issue.