Spline Toolbox

Approximation to Coefficients as Functions of y

Now comes the second step, to get the actual surface. First, extract the coefficients:

• coefsx = fnbrk(spb,'c');
  

Then fit each coefficient vector coefsx(r,:) by a spline of the same order ky and with the same appropriate knot sequence knotsy:

• spb2 = spap2(knotsy,ky,y,coefsx.');
  

Note that, once again, we need to transpose the coefficient array from spb, since spap2 takes the columns of its last input argument as the data values.

Correspondingly, there is now no need to transpose the coefficient array coefsb of the resulting curve:

• coefsb = fnbrk(spb2,'c');
  

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The Bivariate Approximation