It's my first time on Math.stack; be gentle.

I have slider with a range between -1 and 1. If my slider is at 0 I'd expect it to be at 0% If it were at either -1 or 1 I'd expect it to be 100% However it must take into account those won't always be the max & min

When I've got a minimum value of -0.1896362 and maximum value of 0.1383057 I get a bit confused

This is what I've got so far (This is wrong):

percentage = ((slider-minimum)/(maximum-minimum)) *100

I've read this post which is similar to my problem, but the negative numbers are messing things up.

  • $\begingroup$ What is this supposed to be a percentage of? I'm so confused. And gentle. $\endgroup$ – Shahar Mar 20 '14 at 14:40
  • $\begingroup$ If you must know, it's for converting PCM audio data (which ranges between -1 and 1) to a percentile value. $\endgroup$ – Mr Mystery Guest Mar 20 '14 at 14:45
  • $\begingroup$ So you want to know the percent covered from 0 on the bar (i.e. - at x=-0.5, percent = 50%)? $\endgroup$ – Shahar Mar 20 '14 at 14:47
  • $\begingroup$ Shouldn't it go from $0\%$ at the minimum $(-1)$ to $100\%$ at the maximum $(1)$? If so, your equation is fine and you are probably forgetting that minus a negative is plus. If I'm wrong, if the min is not the negative of the max do you truly want $0$ to be $0\%$? $0$ is no longer the center. $\endgroup$ – Ross Millikan Mar 20 '14 at 15:06

Alright, so let's take $u$ to be the upper bound. Lets make $l$ the lower bound. When you go to the right, the percentage of the area swept from x=0 to some $x$ the right is:

$$\frac{x}{u}\times 100\%$$

Similarly, on the left you'll just use your lower bound. You don't even need absolute value because the negatives will cancel:

$$\frac{x}{l}\times 100\%$$

Let me know if that's what you meant.

  • $\begingroup$ So treat upper and lower bound as separate case? That looks good to me. Thank you. $\endgroup$ – Mr Mystery Guest Mar 20 '14 at 15:17

So the slider (call it $x$) goes from 100% at $x=-1$ to 0% at $x=0$ and 100% at $x=1$.

Then use the absolute value function to get these values:

$$\text{percentage} = |x| \cdot 100$$


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.