map()
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, values in-between to values in-between, etc.
Does not constrain values to within the range, because out-of-range values are sometimes intended and useful. The constrain() function may be used either before or after this function, if limits to the ranges are desired.
mapped_value = map(value, fromLow, fromHigh, toLow, toHigh);
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
The mapped value.
Note that the "lower bounds" of either range may be larger or smaller than the "upper bounds" so the map() function may be used to reverse a range of numbers, for example
y = map(x, 1, 50, 50, 1);
The function also handles negative numbers well, so that this example
y = map(x, 1, 50, 50, -100);
is also valid and works well.
The map() function uses integer math so will not generate fractions, when the math might indicate that it should do so. Fractional remainders are truncated, and are not rounded or averaged.
// Map an analog value to 8 bits (0 to 255)
int val = analogRead(A1);
val = map(val, 0, 1023, 0, 255);
analogWrite(PWM1, val);
constrain()
