Bug introduced in 10.3 or earlier and persisting through 12.1.1

When all the points are the same kind, say Integer then NearestNeighborGraph will display a 3D graph when using {x,y,z} coordinates. However, when just one of those points is say a Decimal instead then one sees a 2D graph. It seems the reverse is true too. For example:

allIntegers = NearestNeighborGraph[{{0,0,0},{-1,1,1},{1,-1,1},{-1,-1,1},{1,1,1},{0,0,2},{0,0,1}},{All,2}];
allDecimals = NearestNeighborGraph[{{0.,0.,0.},{-1.,1.,1.},{1.,-1.,1.},{-1.,-1.,1.},{1.,1.,1.},{0.,0.,2.},{0.,0.,1.}},{All,2}];

oneInteger = NearestNeighborGraph[{{0,0.,0.},{-1.,1.,1.},{1.,-1.,1.},{-1.,-1.,1.},{1.,1.,1.},{0.,0.,2.},{0.,0.,1.}},{All,2}];
oneDecimal = NearestNeighborGraph[{{0.,0,0},{-1,1,1},{1,-1,1},{-1,-1,1},{1,1,1},{0,0,2},{0,0,1}},{All,2}];

Row[{allIntegers, allDecimals, oneInteger, oneDecimal}]


2 3D graphs and 2 2D graphs

Is there something I'm doing wrong or some parameter I need to pass? I'd like to be able to force 3D.

  • $\begingroup$ I would call this a bug. Please report it to Wolfram. Note that this is not an official Wolfram website, so the issue won't come to their attention unless you report it. $\endgroup$
    – Szabolcs
    Nov 12 '20 at 10:24
  • 2
    $\begingroup$ Bug reported, lets see what happens. $\endgroup$ Nov 12 '20 at 10:39

One possible workaround to this bug is to set VertexCoordinates explicitly.

pts = {{0., 0, 0}, {-1, 1, 1}, {1, -1, 1}, {-1, -1, 1}, {1, 1, 1}, {0, 0, 2}, {0, 0, 1}};

NearestNeighborGraph[pts, {All, 2}, 
   VertexCoordinates -> pts (* <-- workaround *)]

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