NumScaler

Description

NumScaler will convert for you numbers between ranges using simple linear interpolation. In other words it will scale a number form its source range to a corresponding number within the target range. And vice-versa.

It has three clamping modes that are applied to the input number before conversion, and only if that number is outside its range:

:strict - will raise an exception (default)
:clamp - will cut the number at the edges of the range (e.g. to min or max)
:cycle - will treat the range as circular (think number % range)

It should work correctly for any combination of Integer and Float ranges (note that you can't mix numeric types within a single range, as it doesn't make much sense). It expects common-sense on your part, so trying to use it with empty ranges (e.g. 0..0) is left as undefined (though it might work just as you expect, or not).

All calculations are done internally on Floats so there will be inevitable rounding errors. My tests show that the precision is within 14 decimal places, and therefore that is the default rounding.

There is a pretty brute-force test suite. Should work with any Ruby version.

Applications

Scaling when graphing ...from 0.0..1.0 to 0..(height-1)
Bounded unit conversion ...from Celsius to Fahrenheit, Centimeters to Inches
Circular unit conversion ...from degrees to radians
Value to index mapping ...from 0.0..1.0 to 'very bad' - 'very good'

Examples

Install:

$ gem install numscaler

From the examples/ directory, first some graphing:

require 'numscaler'

s1 = NumScaler.new(0..64, 0.0..Math::PI*2.0)
s2 = NumScaler.new(-1.0..1.0, 0..9)

graph = (0..64).to_a.collect do |e|
  i = s2.from(Math.sin(s1.from(e)))
  a = [' '] * 10
  a[i] = '#'
  a
end

puts graph.transpose.collect {|e| e.join }

Running it will produce a lovely:

                                            #########            
                                        ####         ####        
                                     ###                 ###     
                                   ##                       ##   
                                 ##                           ## 
###                           ###                               #
   ##                       ##                                   
     ###                 ###                                     
        ####         ####                                        
            #########

You can also use it for unit conversion if you wish, like so:

require 'numscaler'

distance = NumScaler.new(0.0..100.0, 0.0..39.3701)
temperature = NumScaler.new(-30.0..120.0, -22.0..248.0)
angle = NumScaler.new(0.0..90.0, 0.0..Math::PI/2.0)

puts 'Distance:'
[
  ['9 mm ammo', 0.9],
  ['max pin distance in an europlug', 1.86],
  ['average baguette length', 65.0],
].each do |label, cm|
  print "#{label} (#{cm} cm) is ".rjust(50)
  puts distance.from(cm).to_s + ' inch'
end

puts "\nTemperature:"
[
  ['siberian cold', -25.0],
  ['minimal workplace temp', 18.0],
  ['usually comfortable', 25.0],
  ['Polish summer', 35.0],
].each do |label, cent|
  print "#{label} (#{cent} Celsius) is ".rjust(50)
  puts temperature.from(cent).to_s + ' Fahrenheit'
end

puts "\nAngle:"
[
  ['human FOV blind spot width', 5.5],
  ['decent slope', 23.0],
  ['in the corner', 90.0],
].each do |label, deg|
  print "#{label} (#{deg} degrees) is ".rjust(50)
  puts angle.from(deg).to_s + ' radians'
end

Which will produce:

Distance:
                            9 mm ammo (0.9 cm) is 0.3543309 inch
      max pin distance in a europlug (1.86 cm) is 0.73228386 inch
             average baguette length (65.0 cm) is 25.590565 inch

Temperature:
                 siberian cold (-25.0 Celsius) is -13.0 Fahrenheit
         minimal workplace temp (18.0 Celsius) is 64.4 Fahrenheit
            usually comfortable (25.0 Celsius) is 77.0 Fahrenheit
                  Polish summer (35.0 Celsius) is 95.0 Fahrenheit

Angle:
      human FOV blind spot width (5.5 degrees) is 0.09599310885969 radians
                   decent slope (23.0 degrees) is 0.4014257279587 radians
                  in the corner (90.0 degrees) is 1.5707963267949 radians

You can also do some esoteric stuff, like:

require 'numscaler'

palette = ' ,-\'"\\O/"\'-. '.split('')
s = NumScaler.new(-1.0..1.0, 0..(palette.length - 1), :mode => :cycle)
c = NumScaler.new(1..32, 0.0..Math::PI*2.0, :mode => :cycle)

1.upto(256) do |o|
  puts "\e[H\e[2J"
  1.upto(32) do |y|
    1.upto(64) do |x|
      print palette[s.from(
        Math.tan(c.from(o)) *\
        (Math.sin(c.from(x)) +\
        Math.cos(c.from(y)))
      )]
    end
    print "\n"
  end
  print "\n"
  sleep(0.5)
end

For this you'd have to run it in a terminal (and it will probably not work as intended on windows).

Copyright

Absolutely no warranty. See LICENSE for details.