# Mapping Values

One common operation is to map values from one range (say, 5 to 10), to another range (say, -35 to 120).  For this, map functions are provided.

Map functions included in the music library, so, in order to use them, you need the following in your program:

```from music import *
```

Map functions are used to expand, contract, or offset data values. They convert a numeric value from one range to another.

For example, mapping the value 0 from the range 0..100 to the range 10..20 results in 10:

```>>> mapValue(0, 0, 100, 10, 20)
10
```

Notice how 0 is the leftmost value in its range, as is 10.

Similarly, mapping 50 from the range 0..100 to the range 10..20 results in 15:

```>>> mapValue(50, 0, 100, 10, 20)
15
```

Again, notice how 50 is in the middle of its range, and so is 15.

So, map functions maintain the relative position of a value.

NOTE:  If you use float numbers, mapValue() will return a float value that is properly scaled (preserving accuracy):

```>>> mapValue(49 , 0, 100, 10, 20)
14
>>> mapValue(49 , 0, 100, 10.0, 20.0)
14.9
```

Notice how in the second example, 49 was mapped to 14.9, since the destination range was float.