Arduino library for fast non-linear mapping or interpolation of values

In Arduino applications often the value of a sensor is mapped upon a more usable value. E.g. the value of analogRead() is mapped onto 0 .. 5.0 Volt. This is done by the map function which does a linear interpolation. This means

 output = C1 + input * C2

As C1 and C2 are to be calculated Arduino has the map() that calculates the two variables runtime from two given mappings.

 output = map(input, I1, I2, O1, O2):

In many cases when there is no linear mapping possible, as the 'points' are not on a single line. One needs non-linear math to calculate the output, Multimap() just does that.

out = Multimap(value, input, output, size) needs two equal sized arrays of reference 'points', input[] and output[], it looks up the input value in the input[] array and if needed it linear interpolates between two points of the output[] array.

• The input[] array must have increasing values, there is no such restriction for the output[] array.
• Multimap() automatically constrains the output to the first and last value in the output[] array.

See examples

Please note the fail example as this shows that in the intern math overflow can happen.

Investigate class implementation for performance.