Matt W-D
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 Jul26 awarded Yearling Nov28 awarded Enlightened Nov28 awarded Nice Answer Sep22 awarded Nice Answer Sep21 awarded Caucus Sep21 awarded Constituent Aug4 awarded Investor Jul29 revised Finding concave hull for separated small clusters edited body Jul29 revised Finding concave hull for separated small clusters deleted 1 characters in body Jul29 answered Finding concave hull for separated small clusters Jul27 comment Finding a Concave Hull @Jay: You know... this is really a separate question. Can you break this out and start a new question? I'll try to give it a shot... Jul27 revised Finding a Concave Hull added 291 characters in body Jul27 comment Finding a Concave Hull @PlatoManiac: I don't see any spikes; what version of Mathematica are you running? (I'm on v8.0.0 myself) Jul27 comment Finding a Concave Hull @Jay: I'm running Mathematica v8.0.0, and I noted that TetGenConvexHull just returns a surface instead of {pts, surface} like your version does. I can't test this, but maybe you could try Show[(Graphics3D[(GraphicsComplex[#1, Polygon[#2]] & ) @@ TetGenConvexHull[#1]] & ) /@ slices] instead of my Show code. Jul27 comment Compact Rational Function Fitting Is it possible to upload some sample data online somewhere, so we can experiment with fitting equations to it? Jul27 comment What does “EquationalLogicFindCounterexample[]” do? This is what I intended. s[k][k] is the identity function in combinatory logic. Back in the 20s when this stuff was being invented, Schoenfinkle and Church treated function application as left associative. I agree that right associativity makes more sense for Mathematica. If you would like a reference, see Schoenfinkle's Building Blocks of Logic (1924), $\S3$. Note that Schoenfinkle wrote "C" instead of "K". Jul27 answered Finding a Concave Hull Jul27 awarded Supporter Jul27 comment What does “EquationalLogicFindCounterexample[]” do? @R.M - Thanks. @ in Mathematica are right-associative, which is a little different than in combinatory logic and lambda calculus (where function application is left associative). So I fixed that... Jul27 revised What does “EquationalLogic`FindCounterexample[]” do? Fixed a typo, added links, fixed combinator logic proof