MATLAB engine for python - How to build graph with weights

2 次查看(过去 30 天)
Hey,
When trying to build the simplest graph on matlab engine with python -
s1 = ['a', 'b', 'c', 'd'];
t1 = ['b', 'c', 'd', 'e'];
w1 = [10, 20, 30, 40];
g = eng.graph(s1,t1,w1);
I'm getting this error-
MatlabExecutionError Traceback (most recent call last)
~\AppData\Local\Temp/ipykernel_15984/3466945527.py in
8 t1 = ['b', 'c', 'd', 'e'];
9 w1 = [10, 20, 30, 40];
---> 10 g = eng.graph(s1,t1,w1);
11
12
c:\Users\amitz\anaconda3\lib\site-packages\matlab\engine\matlabengine.py in __call__(self, *args, **kwargs)
68 return FutureResult(self._engine(), future, nargs, _stdout, _stderr, feval=True)
69 else:
---> 70 return FutureResult(self._engine(), future, nargs, _stdout,
71 _stderr, feval=True).result()
72
c:\Users\amitz\anaconda3\lib\site-packages\matlab\engine\futureresult.py in result(self, timeout)
65 raise TypeError(pythonengine.getMessage('TimeoutCannotBeNegative'))
66
---> 67 return self.__future.result(timeout)
68
69 def cancel(self):
c:\Users\amitz\anaconda3\lib\site-packages\matlab\engine\fevalfuture.py in result(self, timeout)
80 raise TimeoutError(pythonengine.getMessage('MatlabFunctionTimeout'))
...
File C:\Program Files\MATLAB\R2022b\toolbox\matlab\graphfun\+matlab\+internal\+graph\constructFromEdgeList.m, line 256, in constructFromEdgeList
File C:\Program Files\MATLAB\R2022b\toolbox\matlab\graphfun\@graph\graph.m, line 325, in graph.graph
Graph edge weights must be double or single, real, and not sparse
I tried looking everywhere but didn't find the cause.
Really appreciate your assistance.

回答(1 个)

Vinayak Choyyan
Vinayak Choyyan 2023-4-12
Hi Amit,
As per my understanding, you are trying to use the ‘graph()’ function when you are facing an issue with assignment of weight to the graph edges.
‘graph(s,t)’ accepts 2 types of input, namely ‘Node index’ and ‘Node name’. Further, ‘Node name’ type input accepts one of the following types of input for multiple nodes:
  • Cell array of character vectors. Example: {'A' 'B' 'C'}
  • String array. Example: ["A" "B" "C"]
  • Categorical array. categorical(["A" "B" "C"])
Also, in MATLAB, as shown below, the following code results to ‘abcd’ rather than creating an array of characters as you were expecting.
s1 = ['a', 'b', 'c', 'd']
s1 = 'abcd'
Hence you had only created 2 nodes with names ‘abcd’ and ‘bcde’ and were passing the function 4 edge weights instead of 1 edge weight.
s1 = ['a', 'b', 'c', 'd'];
t1 = ['b', 'c', 'd', 'e'];
g = graph(s1,t1);
plot(g)
What you might want to try out is the following,
s2 = {'a', 'b', 'c', 'd'};
t2 = {'b', 'c', 'd', 'e'};
g2 = graph(s2,t2);
plot(g2)
Now you can also assign the 4 weights to the edges respectively.
w1 = [10, 20, 30, 40];
g3 = graph(s2,t2,w1);
plot(g3)
I hope this resolves the issue you were facing.

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