> > But I'd prefer you tell us want you want to do, and then we don't need > to > guess. >
Please look at the following image : http://inspirehep.net/record/833443/files/mst.png These are "minimum spanning tree" (right?) of stars distributed in X (i.e. right ascension, RA) and Y (i.e. declination, DEC). You have this for three open clusters : IC2391, M34, M11. This *is* what I want to do. I want to do a plot like this. I have a list of objects in RA and DEC : alpa (RA) delta (DEC) 0.923 -12.345 0.912 -11.222 0.812 -11.763 0.902 -11.923 0.942 -12.001 ... ... I would like to produce a plot with my list of objects. A plot like the one presented in the link I have provided. More generally, I would like to use MST as a tool to see if the distribution is clustered (e.g. M11, obviously there is a cluster) or homogeneously distributed (e.g. IC 2391, not obvious that there is a cluster). Ultimately, I would like to use the normalised correlation length of the MST (say, "s") and the mean edge length of the MST (say, "m") to make a distinction between overall radial density (m/s > 0.8, most-likely there is a cluster, like for M11) and subclustering (m/s < 0.8, most-likely there are *no* cluster, like for IC 2391). I hope I better explained what I wanted. > > On Wed, Mar 5, 2014 at 9:42 AM, Steve Boudreault > <[email protected]>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 >> -- >> ============================================================ >> Steve Boudreault, Ph.D. >> CNRS UMR 8111 / GÉPI >> Bâtiment 11 - Hipparque Email: [email protected] >> Observatoire de Paris Phone : +33 (0) 145077868 >> 5 Place Jules Janssen Fax: +33 (0) 145077878 >> 92190 Meudon, France Mobile : +33 (0) 604530082 >> ============================================================ >> _______________________________________________ >> igraph-help mailing list >> [email protected] >> https://lists.nongnu.org/mailman/listinfo/igraph-help -- ============================================================ Steve Boudreault, Ph.D. CNRS UMR 8111 / GÉPI Bâtiment 11 - Hipparque Email: [email protected] Observatoire de Paris Phone : +33 (0) 145077868 5 Place Jules Janssen Fax: +33 (0) 145077878 92190 Meudon, France Mobile : +33 (0) 604530082 ============================================================ _______________________________________________ igraph-help mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/igraph-help
