Error Undefined Function 'shortestpath' for input arguments of type 'double'

So I'm working on this code that needs to find the shortest distance between 2 points. I have labelled all the distances as 1 for now but when I run

 path = shortestpath (DG,1,2)

it returns with the error - undefined function......

This is my code

W = [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
DG = sparse ([1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2 3 8 9 4 3 18 17 1 2 3 4 5 8 9 18 17 20 19 18 13 12 17 16 3 4 23 23 23 23 22 22 22 22], [2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 19 18 13 12 7 8 13 14 19 18 13 8 7 12 11 14 15 2 3 8 9 10 13 14 7 6 1 2 19 20 9 10 11 12], W)
path = shortestpath (DG,1,2)

Any help would be appreciated

[Star Strider]

You need to create a digraph object firsty.

However, when I do:

DG = digraph(DG);
path = shortestpath (DG,1,2)

I get this error message:

Error using digraph (line 214)
Adjacency matrix must be square.

I leave that for you to sort.

[Waseem Hussain]

Yeah I've been getting the problem from the start aswell!, I thought I'd use shortest path but like you said there needs to be some sort of graph.

No idea how to fix adjacency matrix must be square

Answer 1

[Walter Roberson]

shortestpath() is defined only for graph and digraph objects. You need to use graph() or digraph() to create a graph before you can shortestpath()

[Walter Roberson]

DG = sparse ([1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2 3 8 9 4 3 18 17 1 2 3 4 5 8 9 18 17 20 19 18 13 12 17 16 3 4 23 23 23 23 22 22 22 22], [2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 19 18 13 12 7 8 13 14 19 18 13 8 7 12 11 14 15 2 3 8 9 10 13 14 7 6 1 2 19 20 9 10 11 12], W, 23, 23);
G = digraph(DG);

[Waseem Hussain]

Thanks for this, it comes up with 23 nodes and 54 edges, is there anyway I can change the labels for the nodes?

[Walter Roberson]

nodenames = {'Gabriel', 'Harvey', 'Chris', 'Warren', 'Irvin', 'Marjorie', 'Walker', 'Adrienne', 'Anne', 'Farmer', 'Larson', 'Garrett', 'Diana', 'Ray', 'Daniel', 'Dawn', 'Montgomery', 'Erick', 'Bass', 'Obrien', 'Leroy', 'Lee', 'Armstrong'};
G = digraph(DG, nodenames);

[Waseem Hussain]

And last question is there a way to reposition nodes, I want it to reposition so that it resembles an extended net of a cube

[Walter Roberson]

See https://www.mathworks.com/help/matlab/ref/graph.plot.html#buzeikk

Answer 2

[Waseem Hussain]

Could you explain to me where 23,23 came from on the last line aswell because I have to write up a report

DG = sparse ([1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2 3 8 9 4 3 18 17 1 2 3 4 5 8 9 18 17 20 19 18 13 12 17 16 3 4 23 23 23 23 22 22 22 22], [2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 19 18 13 12 7 8 13 14 19 18 13 8 7 12 11 14 15 2 3 8 9 10 13 14 7 6 1 2 19 20 9 10 11 12], W, 23, 23)

[Steven Lord]

From the documentation for sparse: "S = sparse(i,j,v) generates a sparse matrix S from the triplets i, j, and v such that S(i(k),j(k)) = v(k). The max(i)-by-max(j) output matrix has space allotted for length(v) nonzero elements."

If you want S to be larger than [max(i) max(j)] in size, you can use sparse to do that as well. Read through the remainder of the documentation for sparse for a description of that syntax.

[Walter Roberson]

The 23 is max() of the two sets of indices you give to sparse -- the maximum node number. You can add a couple of lines of code that would calculate it, but since you are already hard-coding all the node number information you might as well hard-code the 23 as well (that is, better would be if you had assigned the indices to variables in different statements.