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map(-30, -89.75, 89.75, 0, 360)

I'm looking for something like this where:

  • -30 is the input value.
  • -89.75 to 89.75 is the range of possible input values
  • 0 - 360 is the final range to be mapped to

I was told there is a way to do this using http://ruby-doc.org/core-1.9.3/Enumerable.html#method-i-map

.. however its not readily apparent !

carl crott
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1 Answers1

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If I'm understanding correctly, I think you just want to uniformly map one range onto another. So, we just need to calculate how far through the input range it is, and return that fraction of the output range.

def map_range(input, in_low, in_high, out_low, out_high)
  # map onto [0,1] using input range
  frac = (input - in_low) / (in_high-in_low)
  # map onto output range
  frac * (out_high-out_low) + out_low
end

Also, I should note that map has a bit of a different meaning in ruby, and a more appropriate description would probably be transform.

ceyko
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    `Enumerable#map` in Ruby is `std::transform` in C++, but `map` is the standard name for this operation. Not sure why the C++ committee thought it would be a good idea to invent new terminology for existing concepts like `transform` for `map` or `accumulate` for `fold` or "member function" for "method". – Jörg W Mittag Dec 07 '12 at 15:30