Spline coefficients for data point

Dear colleagues,

how can I get the spline coefficients for a certain data point?

I know that I can get all the coefficients by using the point-operator (as "pp.coefs"). But how can I get the coefficients for a specific data point (x value). Is there an automatic expression?

Best regards,

Felix

Answer 1

[Prabhan Purwar]

Hello,

Spline definesa polynomial among the breakpoints in the curve. To define the coefficient at a particular ‘x value’ there is a need to define an interval among enclosed breakpoints and make use of pp.coefs() as suggested.

Refer to the following link for further information:

• https://www.mathworks.com/help/matlab/ref/spline.html
• https://www.mathworks.com/help/curvefit/curve-fitting-toolbox-splines-and-matlab-splines.html

[felix.b]

Thank you, Prabhan!

That's exactly what I did. If someone encounters the same problem, please see the code below.

C = pp.coefs;

b = (pp.breaks)';

j=0;

for k=1:length(C)

if (((xi >= b(k)) && (xi <= b(k+1))) && (j==0))

j=k;

break

end

end

xS1 = b(j);