mapFloat()

Re-maps a number from one range to another. That is, a value of fromLow would get mapped to toLow, a value of fromHigh to toHigh, and values in-between to values in-between, proportionally.

float y = mapFloat(x, 10.0, 50.0, 100.0, 0.0);

The function also handles negative numbers well, so that this example

float y = mapFloat(x, 10.0, 50.0, 100.0, -100.0);

is also valid and works well.

By default, does not constrain output to stay within the [fromHigh, toHigh] range, because out-of-range values are sometimes intended and useful. In order to constrain the return value within range, you can use one of the alternative modes: * the CONSTRAIN mode to simply keep the value within range by restricting extreme values as in constrain() <https://www.arduino.cc/reference/en/language/functions/math/constrain/> * the WRAP mode to wrap the values around as in wrap()

mapFloat(x, 10.0, 50.0, 100.0, -100.0, CONSTRAIN);
mapFloat(x, 10.0, 50.0, 100.0, -100.0, WRAP);

Note

Note that the “lower bounds” (fromLow and toLow) of either range may be larger or smaller than the “upper bounds” (fromHigh and toHigh) so the mapFloat() function may be used to reverse a range of numbers, for example

Unlike the Arduino map() function, mapFloat() uses floating-point math and will generate fractions.

Example

#include <Plaquette.h>

SquareOsc oscillator(1.0);

DigitalOut led(13);

void begin() {
}

void step() {
  // Change frequency between 2Hz and 15Hz over a 30 seconds period, then the frequency will stay at 15Hz.
  float freq = mapFloat(seconds(), 0.0, 30.0, 2.0, 15.0, CONSTRAIN); // try removing CONSTRAIN and see what happens
  oscillator.frequency(freq);

  // Send to LED.
  oscillator >> led;
}

Reference

float pq::mapFloat(double value, double fromLow, double fromHigh, double toLow, double toHigh, uint8_t mode = UNCONSTRAIN)

Re-maps a number from one range to another.

Parameters:

  • value – the number to map

  • fromLow – the lower bound of the value’s current range

  • fromHigh – the upper bound of the value’s current range

  • toLow – the lower bound of the value’s target range

  • toHigh – the upper bound of the value’s target range

  • mode – set to CONSTRAIN to constrain the return value between toLow and toHigh or WRAP for the value to wrap around

Returns:

the mapped value

See Also