Ruby group_by date every 7 days - ruby-on-rails

Question

How can I sort a collection of records by week start and end date? After looking at the strf docs the closest I could get was to group by the week number
weeks = my_data.group_by{|x| x.created_at.strftime('%U %Y') }
{"34 2015"=>
[#<DoctorRecommendation:0x007fd663196ea0
created_at: Tue, 25 Aug 2015 22:29:44 UTC +00:00,
patient_profile_id: 104,],
"33 2015"=>
[#<DoctorRecommendation:0x007fd663194ce0
created_at: Thu, 20 Aug 2015 13:41:37 UTC +00:00,
patient_profile_id: 21,,
#<DoctorRecommendation:0x007fd66319f500
created_at: Tue, 18 Aug 2015 02:47:30 UTC +00:00,
patient_profile_id: 61,
#<DoctorRecommendation:0x007fd66319db38
created_at: Tue, 18 Aug 2015 02:47:29 UTC +00:00,
patient_profile_id: 85,
]
}
I'd rather have the keys be 8/10/2015 - 8/16/2015 and 8/17/2015 - 8/23/2015
There are a couple of issues with this approach. First is that I haven't been able to convert it back to a proper date (tried Date.parse("34 2015")) but received an ArgumentError: invalid date. The second issue with this approach is that certain weeks would be omitted if there were no records.

Answer 1

You can use Rails' date extension to get the beginning and ending of the week (configurable), and use
that to create your range:
weeks = my_data.group_by do |x|
date = x.created_at
left = date.beginning_of_week.strftime('%-m/%-d/%Y')
right = date.end_of_week.strftime('%-m/%-d/%Y')
"#{left} - #{right}"
end

Answer 2

Here's code that does what you want, but with a lot of date parsing. Someone better at Ruby could probably optimize this.
my_data.group_by do |x|
date = Date.parse(x.created_at.strftime("%F"))
monday = date - date.strftime("%u").to_i
sunday = monday + 7
"#{monday.strftime("%F")} - #{sunday.strftime("%F")}"
end
My other suggestion is to query the minimum created_at date and today, generate all of the weeks in between with ruby very quickly, and then do queries. This is slower if you're getting all the data, but much faster if you only need a few of the weeks.