How do I round a float to a specified number of significant digits in Ruby?

Question

It would be nice to have an equivalent of R\'s signif function in Ruby.

For example:

>> (11.11).signif(1)
10
>> (22.22).signif(2)
22
>         


        

Answer 1

Here's an implementation that doesn't use strings or other libraries.

class Float
  def signif(digits)
    return 0 if self.zero?
    self.round(-(Math.log10(self).ceil - digits))
  end
end