# Find the limits of the parameter describing a spline curve (made using cscvn)

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Anshuman Pal on 2 Feb 2022
Answered: Anshuman Pal on 2 Feb 2022
Hello,
I am trying to interpolate a space curve in 3d using splines. This link (https://in.mathworks.com/help/curvefit/splines-in-the-plane.html) shows that the spline is parametrised by a single parameter t, and hence I can evaluate the spline curve at distinct points using fnval(curve, t). However, how do I know the limits (min and max) of this parameter t?
For example, here I plot an incomplete curve (in blue) using an arbitrary max of 100.5 (the min is 0, I presume). The entire curve is plotted in dashed red (see attached file):
curve=cscvn(xyz);
% Evaluate the spline at definite points
t = linspace(0,100.5,501); % 100.5 is arbitrary
cv = fnval(curve, t);
figure; hold on
fnplt(curve,'r--',2) % plot entire spline
plot3(cv(1,:),cv(2,:),cv(3,:),'b','LineWidth',5);
view(3)

Anshuman Pal on 2 Feb 2022
I found the answer! All I had to do was search in the properties of curve. So, I have to use min(curve.breaks) and max(curve.breaks)as the limits of t:
t = linspace(min(curve.breaks), max(curve.breaks),501);

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