How do I add vertex weights?

Questions
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1

This is an extension of a previous question that I asked on this forum. I have an excel file of vertex weights in the first column and their corresponding vertices in the second. The graph comes out as planned, but it is not a weighted graph, as I would expect from the following code:

data = Import["~/Desktop/OHD1.xlsx"]

Graph[Table[Property[data[[1]][[i, 2]], VertexWeight -> data[[1]][[i, 1]]], {i, 1, Length[data[[1]]]}], 
 Table[data[[2]][[i, 1]] \[UndirectedEdge] data[[2]][[i, 2]], {i, 1, Length[data[[2]]]}]]

How do I assign vertex weights? Any response is appreciated.

2

Dear Shawn,

usually a weighted graph is a graph which has weights attached to its edges. See
http://en.wikipedia.org/wiki/Graph_(mathematics)#Weighted_graph

If you want the edges to be weighted you need this:
http://reference.wolfram.com/mathematica/ref/EdgeWeight.html

You can, however, also attach the weights in the way you did to edges. So if you do as you say:

data = Import["~/Desktop/OHD1.xlsx"]

gra = Graph[Table[Property[data[[1]][[i, 2]], VertexWeight -> data[[1]][[i, 1]]], {i, 1, Length[data[[1]]]}], Table[data[[2]][[i, 1]] <-> data[[2]][[i, 2]], {i, 1, Length[data[[2]]]}]]

It looks like this:

Graph1.jpg
Graph1.jpg360×112 6.94 KB

If you then test whether you have a weighted graph:

WeightedGraphQ[gra]

you get True, so For Mathematica this is a weighted graph. Why do you think that it is not a weighted graph?

M.

3

I get the graph and False with the same code.

4

That is very strange. I tried different machines and different versions of Mathematica. I always get True.

ScreenShot2014-07-01at23.14.34.png
ScreenShot2014-07-01at23.14.34.png1406×900 70 KB

Have you tried restarting the kernel/Mathematica?Which version of Mathematica are you running? You should have access to the Wolfram Cloud. Can you try running your code there?

M.

5

I’m running Mathematica 9.0, and I am not sure how to import the data into Wolfram Cloud. I’ve quit the kernel and started again, to no avail.

6

That is strange. I cannot reproduce your problem.

If you want to upload files to the cloud there is a button for that:

ScreenShot2014-07-02at09.38.34.png
ScreenShot2014-07-02at09.38.34.png1232×282 64.5 KB

On the top right there is a button that says “New”; to the right of that you have “an arrow that points up/into the sky/cloud”. You can upload files using that.

Cheers,

Marco

7

The kernel was evaluating locally. I changed it to global, and now the problem is resolved. Thank you for all of your help!