MATLAB: Convert interpolation function to symbolic

data importinterpolationMATLABsymbolic

Hello,
I have a Nx2 .dat file which I import to Matlab as a Nx2 matrix. This .dat file is roughly a collection of [x,y] coordinates of a curve.
What I am trying to do is to obtain not only the curve that intepolates those point but also its form in symbolic code.
My code is the following
clc
clear all
%Importing .dat file and converting to a nx2 matrix
f = fopen('GITT_bi1g20.dat');
data = textscan(f, '%f %f');
data = cell2mat(data); % convert to matrix from cell array
fclose(f);
%Comparison between different interpolation functions
%Polynomial
x = data(:,1);
y = data(:,2);
p = polyfit(x,y,9);
y1 = polyval(p,x);
%pchip() - Hermitian
xx = x;
p = pchip(x,y,xx);
figure(1)
hold on
plot(data(:,1),data(:,2),'m')
plot(xx,p,'--black')
hold off
My biggest wish is actually write the pchip() that intepolates the data points as a symbolic function. (So I can do some Calculus stuff with it and other symbolic functions I am using)
Thanks in advance.

Best Answer

You already get a piecewise polynomial out of pchip. That is a symbolic function - though not on the form expected by the symbolic functions of matlab so not the format you want. Bot look at the form of your final p and you should be able to figure out what to do next.
HTH
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