From what I understand, you are trying to plot contours of different values for the surface defined by ‘sf.mat’. Like you mentioned, the ‘contour’ function cannot be used directly on ‘sf’, but we can recreate the fitted polynomial using the coefficients stored in ‘sf’ and then use the ‘contour’ function to get the isolines. Here’s a simple function to do this:
clc
clear
load 'sf.mat'
figure(1)
plot(sf);
isolines([20,30,40,50],sf)
function isolines(vals,sf)
X = linspace(0,4);
Y = linspace(0,4000);
[x,y] = meshgrid(X,Y);
%Recreating the fitted surface
z = sf.p00 + sf.p10*x + sf.p01*y + sf.p20*x.^2 + sf.p11*x.*y + sf.p02*y.^2 + sf.p21*x.^2.*y + sf.p12*x.*y.^2 + sf.p03*y.^3;
figure(2)
contour(x,y,z,vals);
end
Here are the results:
