GLE Example: bspline.gle

[PDF file]

 

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size 10 8

! http://en.wikipedia.org/wiki/B-spline

sub N j n x
   if n = 0 then
      if (x >= j) and (x < j+1) then return 1
      else return 0
   else
      return (x-j)/n*N(j,n-1,x) + (j+n+1-x)/n*N(j+1,n-1,x)
   end if
end sub

set texlabels 1
begin graph
   scale auto
   title "B-Spline Basis Functions"
   xaxis min 0 max 5 dticks 1 grid
   xticks color gray10
   let d1 = N(0,2,x)
   let d2 = N(1,2,x)
   let d3 = N(2,2,x)
   key pos br
   d1 line color red   key "$b_{0,2}$"
   d2 line color green key "$b_{1,2}$"
   d3 line color blue  key "$b_{2,2}$"
end graph

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