CODEWITHSUNDEEP
c#math
tmighty
tmighty

Reputation: 11389

Normalizing a between 0 and 1 to a given minimum and maximum

I'm dealing with the pitch of a joystick.

This pitch can vary between 0 (all down) and 1 (all up). A pitch of 0.5 would mean that the joystick is in its middle position.

I would like to find a formula that would "map" this pitch to a given minimum and maximum.

The formular would tell me

- that a joystick pitch value of 0 would correspond to a given minimum (let's say -20) 
- that a joystick pitch value of 1 would correspond to a given maximum (let's say 20)
- that a joystick pitch value of 0.5 would correspond to 0 (as it's in the middle of minimum and maximum

I have a black out, I don't find the formula to solve this riddle.

Thank you for the help.

Upvotes: 0

Views: 2037

Answers (3)

adjan
adjan

Reputation: 13652

That's pretty simple, just take the proportion of the distance between max and min and add min:

public double Range(double val, double min, double max)
        =>  min + val * (max - min);

Example usage:

Range(0.0, -20, 20)
Range(0.5, -20, 20)
Range(1.0, -20, 20)

Output

-20
0
20

Upvotes: 2

Carcigenicate
Carcigenicate

Reputation: 45736

This is normally known as the "map range" equation/function. Many graphics libraries come with this as a standard part of the library because of how commonly it's used.

Rosetta Code has implementations in every major language.

The implementation and example for C# is:

using System;
using System.Linq;

public class MapRange
{
    public static void Main() {
        foreach (int i in Enumerable.Range(0, 11))
            Console.WriteLine($"{i} maps to {Map(0, 10, -1, 0, i)}");
    }

    static double Map(double a1, double a2, double b1, double b2, double s) => b1 + (s - a1) * (b2 - b1) / (a2 - a1);
}

Upvotes: 0

Arkku
Arkku

Reputation: 42119

(max - min) * value + min where value is in the range [0,1] should map it to the range [min,max]. In practice there may be some concerns, depending on the programming language† and values, e.g., if min and max are the minimum and maximum of a signed integer type, you cannot compute max - min without overflow in that same type. Using floating point types for all is probably safest.

† When I answered, the question was not tagged with any language, now it is tagged with C# which I am not particularly fluent in.

Upvotes: 1

Related Questions