Re: [igraph] how to plot a very basic MST with igraph

[Gábor Csárdi]

On Wed, Mar 5, 2014 at 9:42 AM, Steve Boudreault <address@hidden> wrote:

Greetings,

I am new to R, and probably this is a very simple problem with very few
things to do. (Sorry if this is the case.)

Here I go ...

I have a list of about 1000 objects in the file "list.csv". It looks like
this :
alpa   delta
0.923   -12.345
0.912   -11.222
0.812   -11.763
0.902   -11.923
0.942   -12.001
...   ...

Alpha is the X axis and delta is the Y axis.

I would like to produce a very simple minimum spanning tree plot, like the
ones I attached with this message.

The informations I got so far using igraph in R implied using an adjacent
matrix (e.g. "G <- graph.adjacency(as.matrix(D), weighted=TRUE)"). Maybe I
miss something important ...

I don't know where you collect your information from, but I would suggest to use the documentation of igraph, e.g. http://igraph.org/r/doc/aaa-igraph-package.html

 

but I fail to understand why I should need a
n x n matrix to make an MST for my list of [X,Y] objects.

Can someone tell me how I can produce a simple minimum spanning tree plot?

Minimum spanning trees are defined for graphs, at least in igraph. What is your graph? A set of points is not a graph.

Maybe you mean that you have a full graph, with your points on the plane as vertices, the weights of the edges are Euclidean distances between pairs or points, and you want the MST of this graph.

But I'd prefer you tell us want you want to do, and then we don't need to guess.

Gabor

Thank you very much for your help.

Best regards,

     Steve Boudreault

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Steve Boudreault, Ph.D.
CNRS UMR 8111 / GÉPI
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