2.4 KiB
MultiMap
Arduino library for fast non-linear mapping or interpolation of values
Description
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 in code:
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 straight line. One needs non-linear math to calculate the output, Multimap() just simulates 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.
Operation
See examples
Please note the fail example as this shows that in the intern math overflow can happen.
Future
- Investigate class implementation for performance / footprint
- flag if input value was "IN_MIN" < input < "IN_MAX", now it is constrained without user being informed.
- extend unit tests
wont
- should the lookup tables be merged into one array of pairs?
- you cannot reuse e.g. the input array then. (memory footprint)