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chapter x. example 1. plotting some b-splines
c from * a practical guide to splines * by c. de boor
calls bsplvb, interv
integer i,j,k,left,leftmk,mflag,n,npoint
real dx,t(10),values(7),x,xl
c dimension, order and knot sequence for spline space are specified...
data n,k /7,3/, t /3*0.,2*1.,3.,4.,3*6./
c b-spline values are initialized to 0., number of evaluation points...
data values /7*0./, npoint /31/
c set leftmost evaluation point xl , and spacing dx to be used...
xl = t(k)
dx = (t(n+1)-t(k))/float(npoint-1)
c
print 600,(i,i=1,5)
600 format(4h1 x,8x,5(1hb,i1,3h(x),7x))
c
do 10 i=1,npoint
x = xl + float(i-1)*dx
c locate x with respect to knot array t .
call interv ( t, n, x, left, mflag )
leftmk = left - k
c get b(i,k)(x) in values(i) , i=1,...,n . k of these,
c viz. b(left-k+1,k)(x), ..., b(left,k)(x), are supplied by
c bsplvb . all others are known to be zero a priori.
call bsplvb ( t, k, 1, x, left, values(leftmk+1) )
c
print 610, x, (values(j),j=3,7)
610 format(f7.3,5f12.7)
c
c zero out the values just computed in preparation for next
c evalulation point .
do 10 j=1,k
10 values(leftmk+j) = 0.
stop
end
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