http://snippets.dzone.com/posts Sat, 26 Jul 2008 20:25:05 GMT DZone Snippets: average code http://snippets.dzone.com/posts/show/4613 Weighted mean ( http://en.wikipedia.org/wiki/Mean#Weighted_arithmetic_mean ) <br /> <br /><code> <br />class Array <br /> #sum (and mean) found on http://snippets.dzone.com/posts/show/2161 <br /> def sum <br /> inject( nil ) { |sum,x| sum ? sum + x.to_f : x.to_f } <br /> end <br /> <br /> def mean <br /> sum.to_f / size <br /> end <br /> <br /> #http://en.wikipedia.org/wiki/Mean#Weighted_arithmetic_mean <br /> def weighted_mean(weights_array) <br /> 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 <br /> w_sum = weights_array.sum <br /> w_prod = 0 <br /> self.each_index {|i| w_prod += self[i] * weights_array[i].to_f} <br /> w_prod.to_f / w_sum.to_f <br /> end <br />end <br /></code> <br /> <br />Example <br /><code> <br />>> a = [1,2,3] <br />=> [1, 2, 3] <br />>> w = [1,1,1] <br />=> [1, 1, 1] <br />>> a.weighted_arithmetic_mean(w) <br />=> 2.0 <br />>> a.mean <br />=> 2.0 <br />>> w = [5,2,1] <br />=> [5, 2, 1] <br />>> a.weighted_arithmetic_mean(w) <br />=> 1.5 <br /></code> Wed, 03 Oct 2007 21:29:12 GMT http://snippets.dzone.com/posts/show/4613 wiseleyb (ben) http://snippets.dzone.com/posts/show/2631 Split a string into an array of roughly equal sized chunks based on a string or regular expression delimiter. <br />Delimiter is preserved in output. <br /> <br /><code> <br />class String <br /> def chunk_string(average_segment_size = 40, sclice_on = /\s+/) <br /> out = [] <br /> slices_estimate = self.size.divmod(average_segment_size) <br /> slice_count = (slices_estimate[1] > 0 ? slices_estimate[0] + 1 : slices_estimate[0]) <br /> slice_guess = self.size / slice_count <br /> previous_slice_location = 0 <br /> (1..slice_count - 1).each do <br /> |i| <br /> slice_location = self.nearest_split(slice_guess * i, sclice_on) <br /> out << self.slice(previous_slice_location..slice_location) <br /> previous_slice_location = slice_location + 1 <br /> end <br /> out << self.slice(previous_slice_location..self.size) <br /> out <br /> end <br /> <br /> def nearest_split(slice_start, slice_on) <br /> left_scan_location = (self.slice(0..slice_start).rindex(slice_on)).to_i <br /> right_scan_location = (self.slice((slice_start+1)..self.size).index(slice_on)).to_i + slice_start <br /> ((slice_start - left_scan_location) < (right_scan_location - slice_start) ? left_scan_location : right_scan_location) <br /> end <br />end <br /></code> Thu, 21 Sep 2006 00:29:28 GMT http://snippets.dzone.com/posts/show/2631 duncanbeevers (Duncan Beevers)