arduino实用数学函数之map()

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.

把一个数从一个范围变换到另一个范围。


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.

不会把值强制限制在范围之内，因为超范围的值经常也是有用的。如果需要的范围做一限制。可以在这个函数之前或之后使用constrain() 函数。


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

注意，两个范围中的“下界”要比“上界”大或下，这样map（）可以用来反转一个范围，例如


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


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

函数也可以处理负数，例如


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


is also valid and works well.

也有效和正确


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（）函数使用整型，所以不会产生分数，分数将会被截去，并不是全面的或平均值（？）

Parameters 参数

value: the number to map

给map的值


fromLow: the lower bound of the value's current range

值现在的下界


fromHigh: the upper bound of the value's current range

值现在的上界


toLow: the lower bound of the value's target range

值目标范围的下界


toHigh: the upper bound of the value's target range

值目标范围的上界

Returns 返回值

The mapped value.

映射的值

Example


void setup() {}

void loop()
{
int val = analogRead(0); //读取0口的值
val = map(val, 0, 1023, 0, 255);//从0-1023映射到0-255
analogWrite(9, val);//把映射后的值写给9口
}

Appendix 附录

For the mathematically inclined, here's the whole function

对于数学上来说,这是整个函数

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;
}