Rounding float in Ruby

Question

I\'m having problems rounding. I have a float, which I want to round to the hundredth of a decimal. However, I can only use .round which basically turns it in

Answer 1

You can add a method in Float Class, I learnt this from stackoverflow:

class Float
    def precision(p)
        # Make sure the precision level is actually an integer and > 0
        raise ArgumentError, "#{p} is an invalid precision level. Valid ranges are integers > 0." unless p.class == Fixnum or p < 0
        # Special case for 0 precision so it returns a Fixnum and thus doesn't have a trailing .0
        return self.round if p == 0
        # Standard case  
        return (self * 10**p).round.to_f / 10**p
    end
end

Answer 2

If you just need to display it, I would use the number_with_precision helper. If you need it somewhere else I would use, as Steve Weet pointed, the round method

Answer 3

For ruby 1.8.7 you could add the following to your code:

class Float
    alias oldround:round
    def round(precision = nil)
        if precision.nil?
            return self
        else
            return ((self * 10**precision).oldround.to_f) / (10**precision)
        end 
    end 
end

Answer 4

Pass an argument to round containing the number of decimal places to round to

>> 2.3465.round
=> 2
>> 2.3465.round(2)
=> 2.35
>> 2.3465.round(3)
=> 2.347

Answer 5

When displaying, you can use (for example)

>> '%.2f' % 2.3465
=> "2.35"

If you want to store it rounded, you can use

>> (2.3465*100).round / 100.0
=> 2.35

Answer 6

def rounding(float,precision)
    return ((float * 10**precision).round.to_f) / (10**precision)
end