Normalizing dataset with ruby

I have a data set that ranges from 1 to 30,000

I want to normalize it, so that it becomes 0.1 to 10

What is the best method/function to do that?

Would greatly appreciate it if you could give some sample code!

Solution

Here's a code snippet, assuming you want a linear normalization. It's a very simplistic version (just straight code, no methods), so you can see "how it works" and can apply it to anything.

xmin = 1.0
xmax = 30000.0
ymin = 0.1
ymax = 10.0

xrange = xmax-xmin
yrange = ymax-ymin

y = ymin + (x-xmin) * (yrange / xrange)

And here it is done as a function:

def normalise(x, xmin, xmax, ymin, ymax)
  xrange = xmax - xmin
  yrange = ymax - ymin
  ymin + (x - xmin) * (yrange.to_f / xrange) 
end

puts normalise(2000, 1, 30000, 0.1, 10)

(Note: the to_f ensures we don't fall into the black hole of integer division)