[Laplacian function in Matlab2017] Undefined function 'laplacian' for input arguments of type 'double'.

Hello,

What is wrong with the following code. I got an input error argument for laplacian.

n = 1000;
x = randperm(n);
gs = 450; group1 = x(1:gs);  group2 = x(gs+1:end);
p_group1 = 0.5; p_group2 = 0.4; p_between = 0.1;
A(group1, group1) = rand(gs,gs) < p_group1;
A(group2, group2) = rand(n-gs,n-gs) < p_group2;
A(group1, group2) = rand(gs, n-gs) < p_between;
A = triu(A,1);
A = A + A';
spy(A);
L = laplacian(A);

I got the following error :

Undefined function 'laplacian' for input arguments of type 'double'.

l'm using Matlab2017b

Thank you

Answer 1

[Steven Lord]

I suspect you're trying to call this function. If so the input must be a graph object, not simply an adjacency matrix. Create a graph object using A then pass that graph object into laplacian.

[AHMED MAZARI]

l'm trying to reproduce this result https://www.cs.purdue.edu/homes/dgleich/demos/matlab/spectral/spectral.html#meaningful

see Finding a Partition. Just called the laplacian with only an adjacency matrix

[Christine Tobler]

David Gleich wrote the package MatlabBGL, perhaps this contains a laplacian function? It's not a standard MATLAB function.

[AHMED MAZARI]

I just checked it doesn't contain a laplacian function

[AHMED MAZARI]

@ Steven Lord, is there a way to get a graph object from my adjacency matrix A ?

[Steven Lord]

From the second link I posted:

"G = graph(A) creates a weighted graph using a square, symmetric adjacency matrix, A."