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Student Support Forum: 'ComplexInfinity during D[BSplineBasis,...]' topicStudent Support Forum > General > "ComplexInfinity during D[BSplineBasis,...]"

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Rhys Ulerich
03/31/11 7:19pm

Atop Mathematica 7.0.2.0 I see incorrect ComplexInfinity's arise when evaluating the derivatives of BSplineBasis functions.

Run the following snippet

d=2;
knots={0, 0,0,1,2,3,3,3};
n= Length[knots]-d-2;
B=BSplineBasis[{d,knots},#1,#2]&;
Plot[Table[B[i,x],{i,0,n}],{x,First[knots],Last[knots]}]
Table[D[B[i,x],x],{i,0,n}]

and observe that the first and last entry of the table are ComplexInfinity. BSplineBasis should allow symbolic differentiation of the first and last basis function for a given set of knots.

Thanks,
Rhys

[This was corrected in 8.0 - Forum Moderator]

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