Hi every one, I am a little bit new in matlab I would like to generate directed random graph using Matlab. That is a random directed graph with n nodes . That is How to generate a random network with a certain number of nodes in Matlab

[G]= function(n) . . . return

Answer 1

[Guillaume]

With so little information the only thing we can do is point you to digraph. What is random about your graph? Is the number of edges fixed.

g = digraph(randi([0 n], n))

will generate a random directed graph with n node. It's unlikely to be pretty as it will have many edges (n*(n-1) edges on average).

[M Shaka]

thanks for your answer. I meant that generating a random graph with a certain number of nodes. The number of edges must be also random. For example with 5 nodes the number of edges can be 1 or 2 or even 10, 15 and etc. Just the number of nodes is fixed.

[Guillaume]

Well, then as I have said

g = digraph(randi([0 n], n))

will generate a random directed graph with n node with on average n*(n-1) edges.

Another option,

g = digraph(max(randi([-n n], n), 0))

which will generate a random directed graph with n node with on average n*(n/2-1) edges.

There are plenty of other ways you could generate random digraphs.

[M Shaka]

just one more question. this command is for matlab 2017. Isn't it? Unfortunately I use matlab 2014.

[Guillaume]

As per the doc (link in my answer) digraph requires at least R2015b.

If you want to work with graphs, I strongly recommend upgrading to at least R2015b as it introduced lots of graph functions including the ability of easily plotting graphs.

For example, in just two lines:

g = digraph(max(randi([-60 10], 10), 0));
plot(g);

I've generated this:

[Steven Lord]

FYI the sprand and sprandsym functions are also useful in generating random networks. That may be an easier to understand alternative than calling max(randi(... to generate a matrix with roughly a specific proportion of nonzero elements.

Answer 2

[M Shaka]

thanks