piecewise linear mapping is nothing making nonlinear graph to linear one ,,this can be done by deviding the nonlinear graphs into collection of linear ones.
Indeed, it's a very usefull technique if you are writing software in assembler, as coding 3 linear sections is much easier than writing some nasty mathematical functions. (Especially if you are trying to get by with 8 or 16 bit arithmetic)
Lookup tables are also a very fine thing....
Del
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