Hello Felix, the geometry is returned as an incidence graph in GRAPE format. For each vertex x of that graph, Adjacency(haemers, x) will give you its neighbours. From that you can reconstruct the adjacency matrix if you want.
For example with the following function: AdjacencyMatrix := function ( gamma ) local result, x, y; result := NullMat( gamma.order, gamma.order ); for x in [ 1 .. gamma.order ] do for y in Adjacency( gamma, x ) do result[x][y] := 1; od; od; return result; end However it could be worth your while working with the graph format as it is. "delta" just refers to the incidence graph. PartialLinearSpaces returns a list of those. Hope this helps, Sven Reichard Institut für Algebra TU Dresden On 01/21/2015 01:33 PM, Felix Goldberg wrote: > Hello all, > > I am running the code in the example in Section 9.2 of the GRAPE manual ( > http://www.maths.qmul.ac.uk/~leonard/grape/manual/CHAP009.htm) , which > generates the Haemers partial geometry pg(4,17,2). > > All works well but I cannot understand where exactly the incidence matrix > is stored and how to access it. The manual (referred to above) says that > there is a *delta* associated to the geometry output by the function > PartialLinearSpaces > but I can't find it. > > I tried to run RecNames on the output (the variable called *haemers*) and > got this: > > [ "names", "group", "order", "representatives", "isSimple", "isGraph", > "schreierVector", "adjacencies" ] > > No sign of *delta* and apparently no incidence matrix. > > Any help will be greatly appreciated. > > Thanks, > Felix > > > >
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