After using Matlab on Spline fitting, l have plotted a curve that are composed by a set of 3D points. But l cannot find the function of this curve if you can help? Thanks
Have you been using the curve fitting toolbox?
If so, 'cscvn' returns the splines in a piecewise polynomial structure (ppform https://uk.mathworks.com/help/curvefit/constructing-and-working-with-ppform-splines.html).
If you examine the 'coefs' property it will give you an array that corresponds to the coefficients of each power in the characteristic polynomial. There's a very good stack overflow post on this very topic here: https://stackoverflow.com/questions/18976289/piecewise-equations-for-spline
a 'cscvn(.)' function is recommended to tackle your problem. You may get a struct type data which store coefficients of piecewise polynimals. The number of rows of coefficients depends on the amount of points for your interpolation.
take 2D interpolation for illustration, if ncs = cscvn (points).
suppose you have 5 knots, you could get 4 segments.
%--------------------------------------------------------------------------------------
for i=1:1:ncs.pieces % ncs.pieces=4 in this case
T = ncs.breaks(i+1) - ncs.breaks(i);
% T is the chord length
x = ppmak([0 T],ncs.coefs(2*i-1,:));
% x is the x-coordinate of points on the i-th segment
y = ppmak([0 T],ncs.coefs(2*i,:));
% y is the y-coordinate of points on the i-th segment
end
%--------------------------------------------------------------------------------------
- Badges
- Science topic