Ruby 按日期计算项目

Question

我有一个日期数组，例如

Fri Jan 28 10:13:19 UTC 2011
Thu Jan 27 16:57:59 UTC 2011
Thu Jan 27 16:41:21 UTC 2011
Wed Jan 26 09:20:48 UTC 2011
Mon Jan 24 16:19:48 UTC 2011
Fri Jan 21 11:45:34 UTC 2011
Fri Jan 21 11:42:19 UTC 2011

我如何对它们进行分组，以便输出与每天的项目计数一样:

Friday 28 => 1
Thursday 27 => 2
Wednesday 26 => 1
Monday 24 => 1
Friday 21 => 2

Answer 1

或者，更详细地介绍 kurumi 的解决方案并使用 Jimmy 的 strftime:

histogram = dates.inject(Hash.new(0)) do |hist, date|
  hist[date.strftime('%A %d')] += 1
  hist 
end.sort_by{|date, count| date.split(' ').last}.reverse

给我们:

Friday 28: 1
Thursday 27: 2
Wednesday 26: 1
Monday 24: 1
Friday 21: 2

好吗？