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Re: BSpline function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112827] Re: BSpline function
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 2 Oct 2010 05:44:50 -0400 (EDT)

pts = {{0.3, 0.74152}, {0.4, 0.650256},
   {0.5, 0.588225}, {0.6, 0.541167},
   {0.8, 0.473432}, {1., 0.425661},
   {1.022, 0.42067}, {1.25, 0.380029},
   {1.5, 0.346518}, {2., 0.300173},
   {2.044, 0.297321}};

f = BSplineFunction[pts, SplineDegree -> 5];

ParametricPlot[f[t], {t, 0, 1}]

Clear[g]

g[t_?NumericQ] := f[t][[1]]

NMinimize[{Abs[g[t] - 0.9],
   0 < t < 1}, t][[2]]

{t -> 0.430445}

FindRoot[g[t] == 0.9, {t, .4}]

{t -> 0.430445}

f[t] /. %

{0.9, 0.450758}


Bob Hanlon

---- eric g <eric.phys at gmail.com> wrote: 

=============
hello Group,
I want to find the parameter of the spline function @ x=.9 in order to 
find the appropriate value of y?
I can eye ball it using Table [{t,f[t]},{t,0,1,.01}] but I would like to 
get it straihgt...
Also I would like to know what is the appropriate Spline-degree I should 
use?
thnks in advance,
Eric

pts={{0.3, 0.74152}, {0.4, 0.650256}, {0.5, 0.588225}, {0.6,
   0.541167}, {0.8, 0.473432}, {1., 0.425661}, {1.022, 0.42067}, {1.25,
    0.380029}, {1.5, 0.346518}, {2., 0.300173}, {2.044, 0.297321}};
f= BSplineFunction[pts,SplineDegree->5];

f[?]={0.9,?}



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