Map a custom portion of 360 degress to an float from 0 to 1

Question

I'm getting input from 0 to 360 from my sensor. But I want to map things so 340 degrees equals 0 and 20 degrees equals 1.

I've tried doing things like using the map function

float myInput = readData();
float  myVar = map(myInput, 0, 360, 0, 1);

But that just makes 340 higher than 20. I think the fact that it goes from 340 to 0 and then to 20 is what's complicating things. Is there a way to map a custom portion of 360 degrees from 0 to 1 when my lower point would have a higher number than the higher point?

Answer 1

You could convert your input to a different range first. Something like this:

if(myInput > 180) {
  myInput = myInput - 360;
}

That will convert values like 340 to -20. So now your input range is -20 to 20 and you can use the map function:

float mappedInput = map(myInput, -20, 20, 0, 1);

You haven't said what should happen if your input is outside that range, so you might have to think harder about those cases, but the general approach should work.