It is interesting that the MATLAB utilities that I seem to use a lot ( besides those for filter design like FIR1, REMEZ and so on) are SPLINE, POLYFIT and POLYVAL. I typically use these for fitting x-y data for approximations of various measurements. In addition the identities based on INTERP are also very useful and can be used with the fitting utilities mentioned above. MATLAB has extensive documentation on these and their multiple options.

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