How to Map a Range to -1 to 1 in Relationships?

[SLSCoder]

I have a number, the high, that could be positive, negative or zero and can be a fraction.
I have another number, the low, that could also be positive, negative or zero and can be a fraction.
I have another number, the variable that is between the high and the low.

It is safe to say that the high is greater than the low.
I need to represent the high as 1 and the low as -1.
Then I need to determine what the variable value would be (between 1 and -1).

How can I solve this?

 

[romsek]

$$\text{So you are mapping the interval $[low,~high]$ to the interval $[-1,1]$}\\
\text{Let $x$ be your variable that you want to transform, and $\tilde{x}$ be it's new value}\\
\text{It's assumed that $low \leq x \leq high$}\\~\\
\tilde{x} = -1 + 2\dfrac{x-low}{high - low},~ -1 \leq \tilde{x} \leq 1$$

 

[SLSCoder]

Thank you!
I need to write this function in code (software).
My math is pretty bad so I just want to clarify that the equation looks like this?

This is correct: low ≤ x ≤ high

-1 + 2 * ((X - lo) / (hi - lo));

I sure appreciate your help.

 

[romsek]

looks good if your variables are now called hi and lo