It is sometimes argued that MOND is a bad/flexible theory because the interpolation function which joins together the four limits of MOND (Newtonian, Milgromian, Quasi-Newtonian and Forced-Newtonian) can be manually chosen from any number of equations. There is indeed an infinite number of equations one can use to accomplish this. However one must always obey the limits of MOND and one does not want to use an interpolation function that is overly complex. Therefore the literature on MOND almost exclusively only uses three interpolation functions which, as can be seen in the graph below do not differ all that much (about 10% around a0).
Particularly if we look at the planets and the binned data from both galaxy kinematics and galaxy weak gravitational lensing we see that the area where the influence of choosing one interpolation function over the other is relevant is a very small part of the available range of the data.
The most common interpolation functions (IFs) are the simple, standard and RAR (radial acceleration relation) interpolation functions.
Simple:
Standard:
RAR:
No analytical expression for the RAR μ function exists. It can however be determined numerically by inverting its ν function.
Continental Hotspot 
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