DZone Snippets: sum code

Using the XSLT sum function

jrobertson (James Robertson) — Sat, 12 Jan 2008 11:41:08 GMT

This XML and XSLT code is an example of storing and displaying a car mileage log. Notably the XSLT sum() function displays the total no of miles.

file: car_log.xsl







    

      

    

            

        Total miles this month: 

        

      

    

    

    

    

      

        trip

        

          

        

          

        miles

        

          

        

          

        description

file: car_log.xml





  

    car_log

  

  

    Wed Dec 12 20:00:33 +0000 2007trip to the supermarket11.8my first trip with the GPS installed

    Fri Dec 14 11:45:09 +0000 2007driving around the park26.1

    Thu Dec 20 01:21:27 +0000 2007trip to the supermarket 8.5

    Thu Dec 20 01:34:26 +0000 2007visiting parents12.7

output



Total miles this month: 59.1

...

Weighted Mean

wiseleyb (ben) — Wed, 03 Oct 2007 21:29:12 GMT

Weighted mean ( http://en.wikipedia.org/wiki/Mean#Weighted_arithmetic_mean )



class Array

  #sum (and mean) found on http://snippets.dzone.com/posts/show/2161

  def sum

    inject( nil ) { |sum,x| sum ? sum + x.to_f : x.to_f }

  end

  

  def mean

    sum.to_f / size

  end

  

  #http://en.wikipedia.org/wiki/Mean#Weighted_arithmetic_mean

  def weighted_mean(weights_array)

    raise "Each element of the array must have an accompanying weight.  Array length = #{self.size} versus Weights length = #{weights_array.size}" if weights_array.size != self.size

    w_sum = weights_array.sum

    w_prod = 0

    self.each_index {|i| w_prod += self[i] * weights_array[i].to_f}

    w_prod.to_f / w_sum.to_f

  end

end

Example



>> a = [1,2,3]

=> [1, 2, 3]

>> w = [1,1,1]

=> [1, 1, 1]

>> a.weighted_arithmetic_mean(w)

=> 2.0

>> a.mean

=> 2.0

>> w = [5,2,1]

=> [5, 2, 1]

>> a.weighted_arithmetic_mean(w)

=> 1.5

days-up-to-month - returns the number of days in a year, preceding the given month.

gregg.irwin (Gregg Irwin) — Wed, 13 Dec 2006 03:13:00 GMT



days-in-months: [31 28 31 30 31 30 31 31 30 31 30 31]

days-in-months-leap: head change at copy days-in-months 2 29



days-up-to-month: func [month /in year] [

    sum copy/part either leap-year?/with any [year now] [days-in-months-leap] [days-in-months] month - 1

]

Generic 'sum' and 'mean' methods for Ruby arrays

peter (Peter Cooperx) — Thu, 08 Jun 2006 20:19:04 GMT

class Array; def sum; inject( nil ) { |sum,x| sum ? sum+x : x }; end; end

It's class agnostic, so you can do this:

[1,2,3].sum              # => 6

['a','b','c'].sum        # => 'abc'

[['a'], ['b','c']].sum   # => ['a', 'b', 'c']

You can then add a 'mean' operator easily:

class Array; def mean; sum / size; end; end

mean only works for numbers though, of course, like so:

[1,2,1000].mean # => 334

That said, if your class implements division, it'll also work!