Reference.Map History

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August 24, 2012, at 11:51 PM by Scott Fitzgerald -
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February 06, 2010, at 09:26 AM by David A. Mellis -
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February 06, 2010, at 03:20 AM by Paul Badger -
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August 04, 2008, at 09:03 PM by Paul Badger -
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The function also handles negative numbers well so this example

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

August 04, 2008, at 05:55 AM by Paul Badger -
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y = map(x, 1, 50, -50, -100);

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y = map(x, 1, 50, 50, -100);

August 04, 2008, at 05:55 AM by Paul Badger -
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Examples

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Example

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/* Map an analog value to 8 bits (0 to 255) */

August 04, 2008, at 05:53 AM by Paul Badger -
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August 04, 2008, at 05:51 AM by Paul Badger -
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The map() function uses integer math so will not generate fractions, when the math might indicate that is should do so. Fractional remainders are truncated, and are not rounded or averaged.

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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.

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August 04, 2008, at 05:50 AM by Paul Badger -
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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 constrained ranges are desired.

Note that the "lower bounds" of either range may be larger or smaller than the "upper bounds" so the function may be used to reverse a range of numbers, for example

to:

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.

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

August 04, 2008, at 05:47 AM by Paul Badger -
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Note that the lower and upper bounds are just markers that define the ranges

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August 04, 2008, at 05:47 AM by Paul Badger -
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Note that the "lower bounds" of either range may be larger or smaller than the "upper bounds" so the 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 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 is should do so. Fractional remainders are truncated, and are not rounded or averaged.

Added lines 49-54:

Note that the lower and upper bounds are just markers that define the ranges

August 04, 2008, at 05:30 AM by Paul Badger -
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Does not constrain values to within the range, because out-of-range values are sometimes intended and useful.

to:

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 constrained ranges are desired.

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Example

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Examples

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Apendix

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Appendix

August 03, 2008, at 08:35 PM by Paul Badger -
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August 03, 2008, at 08:34 PM by Paul Badger -
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Apendix

For the mathematically inclined, here's the whole function

long map(long x, long in_min, long in_max, long out_min, long out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

April 23, 2008, at 06:44 AM by Paul Badger -
Changed lines 7-8 from:

Does not constrain values to within the range, because out-of-range values are something intended and useful.

to:

Does not constrain values to within the range, because out-of-range values are sometimes intended and useful.

March 29, 2008, at 03:31 PM by David A. Mellis -
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Example

void setup() {}

void loop()
{
  int val = analogRead(0);
  val = map(val, 0, 1023, 0, 255);
  analogWrite(9, val);
}

March 29, 2008, at 03:15 PM by David A. Mellis -
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map(value, fromLow, fromHigh, toLow, toHigh)

Description

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 something intended and useful.

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

Returns

The mapped value.

See Also

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