How to group Date and time data from API

Question

I am trying to group data I am getting from an API to serve to our front application. I mean group "time" by "date". dates: {date1: [time1, time2, timeN], date2: [time1...]}

My input is like this:

{"date"=>"2017-04-04T00:00:00", "time"=>"1754-01-01T13:00:00"}
{"date"=>"2017-04-04T00:00:00", "time"=>"1754-01-01T14:00:00"}
{"date"=>"2017-04-05T00:00:00", "time"=>"1754-01-01T12:00:00"}
{"date"=>"2017-04-05T00:00:00", "time"=>"1754-01-01T13:00:00"}

And my output should be like this:

dates: [{date: "2017-04-04T00:00:00", availableTimes: ["1754-01-01T13:00:00", "1754-01-01T14:00:00"]}, {date: "2017-04-05T00:00:00", availableTimes: ["1754-01-01T12:00:00", "1754-01-01T13:00:00"]}]

I am trying to do this this way but without going into loop madness. I have the following:

dates  = Hash[input_data.map{|sd| [sd.date, [""]]}]

This gives me the data outpout like this:

{"2017-04-04T00:00:00"=>[""],
 "2017-04-05T00:00:00"=>[""],
 "2017-04-11T00:00:00"=>[""],
 "2017-04-12T00:00:00"=>[""],
 "2017-04-18T00:00:00"=>[""],
 "2017-04-19T00:00:00"=>[""],
 "2017-04-25T00:00:00"=>[""],
 "2017-04-26T00:00:00"=>[""]}

Just curious : what is this time format? What's `1754-01-01`? — Eric Duminil, Apr 10 '17 at 21:15
Actually I do not know, just receive this info from API, it is dummy data at the moment so that could be why the date is like 1754 :P — Nikos4Life, Apr 17 '17 at 08:54

Ilya · Answer 1 · 2017-04-10T19:41:34.130

Just one possible way:

input.each_with_object(Hash.new { |h, k| h[k] = [] }) do |h, m|
  m[h['date']] << h['time']
end.map { |k, v| { date: k, avaliable_times: v } }
#=> [{:date=>"2017-04-04T00:00:00", :avaliable_times=>["1754-01-01T13:00:00", "1754-01-01T14:00:00"]},
#    {:date=>"2017-04-05T00:00:00", :avaliable_times=>["1754-01-01T12:00:00", "1754-01-01T13:00:00"]}]

Actually, it seems like your data structure would be more concise without last map, I mean:

#=> {"2017-04-04T00:00:00"=>["1754-01-01T13:00:00", "1754-01-01T14:00:00"],
#    "2017-04-05T00:00:00"=>["1754-01-01T12:00:00", "1754-01-01T13:00:00"]}

Indeed. The second format would be much easier/faster to work with. — Eric Duminil, Apr 10 '17 at 21:19

score 1 · Answer 2 · answered Apr 10 '17 at 19:33

1

There is many ways you can do this, one way is to create a new hash, and set the default value to be an array, then loop over the results and insert the dates:

dates = Hash.new { |hash, key| hash[key] = [] }
input_data.each{ |sd| dates[sd["date"]] << sd["time"] }

answered Apr 10 '17 at 19:33

Lasse Sviland

1,479
11
23

This returns `{"2017-04-04T00:00:00"=>["1754-01-01T13:00:00", "1754-01-01T14:00:00"], "2017-04-05T00:00:00"=>["1754-01-01T12:00:00", "1754-01-01T13:00:00"]}`, which is not the required format. Also, it should be noted that this does not return the new value of `dates`. If, for example, it were wrapped in a method, you'd need a final line `dates`. – Cary Swoveland Apr 10 '17 at 23:47
I'd recommend getting familiar with `each_with_object`. – the Tin Man Apr 18 '17 at 21:38

score 1 · Accepted Answer · answered Apr 10 '17 at 19:42

You are getting that output because your map function is not actually modifying any sort of data structure. It is simply returning a new array full of arrays that contain the date and an array with an empty string. Basically, this isn't going to be done with just a single map call.

So, the basic algorithm would be:

Find array of all unique dates
Loop through unique dates and use select to only get the date/time pairs for the current date in the loop iteration
Set up the data in the format you prefer

This code will have filteredDates be in the format you need the data

filteredDates = { dates: [] }
uniqueDates = input_data.map { |d| d["date"] }.uniq # This is an array of only unique dates
uniqueDates.each do |date|
    dateTimes = input_data.select { |d| d["date"] == date }
    newObj = { date: date }
    newObj[:availableTimes] = dateTimes.map { |d| d["time"] }
    filteredDates[:dates].push(newObj)
end

Here is what filteredDates will look like:

{:dates=>[{:date=>"2017-04-04T00:00:00", :availableTimes=>["1754-01-01T13:00:00", "1754-01-01T14:00:00"]}, {:date=>"2017-04-05T00:00:00", :availableTimes=>["1754-01-01T12:00:00", "1754-01-01T13:00:00"]}]}

Cary Swoveland · Answer 4 · 2017-04-11T01:26:54.660

I would use Enumerable#group_by.

dates = [{"date"=>"2017-04-04T00:00:00", "time"=>"1754-01-01T13:00:00"},
         {"date"=>"2017-04-04T00:00:00", "time"=>"1754-01-01T14:00:00"},
         {"date"=>"2017-04-05T00:00:00", "time"=>"1754-01-01T12:00:00"},
         {"date"=>"2017-04-05T00:00:00", "time"=>"1754-01-01T13:00:00"}]

dates.group_by { |g| g["date"] }.
      map { |k,v| { date: k, available_times: v.map { |h| h["time"] } } }
  #=> [{:date=>"2017-04-04T00:00:00",
  #     :available_times=>["1754-01-01T13:00:00", "1754-01-01T14:00:00"]},
  #    {:date=>"2017-04-05T00:00:00",
  #     :available_times=>["1754-01-01T12:00:00", "1754-01-01T13:00:00"]}]

The first step produces the following intermediate value:

dates.group_by { |g| g["date"] }      
  #=> {"2017-04-04T00:00:00"=>
  #     [{"date"=>"2017-04-04T00:00:00", "time"=>"1754-01-01T13:00:00"},
  #      {"date"=>"2017-04-04T00:00:00", "time"=>"1754-01-01T14:00:00"}],
  #    "2017-04-05T00:00:00"=>
  #     [{"date"=>"2017-04-05T00:00:00", "time"=>"1754-01-01T12:00:00"},
  #      {"date"=>"2017-04-05T00:00:00", "time"=>"1754-01-01T13:00:00"}]}

I also thought about `group_by` but was confused by using nested `map` :). — Ilya, Apr 11 '17 at 06:06

whodini9 · Answer 5 · 2017-04-10T19:55:20.720

0

There are probably more elegant ways, but

results = Hash.new
dates.each do |date|
  d, t = date['date'].split('T') # (clean up/split date and time formatting)
  results.key?(d) ? nil : results[d] = Array.new
  results[d] << t
end
puts results
# => {"2017-04-04"=>["13:00:00", "14:00:00"], "2017-04-05"=>["12:00:00", "13:00:00"]}

edited Apr 10 '17 at 19:55

answered Apr 10 '17 at 19:33

whodini9

1,434
13
18

How to group Date and time data from API

5 Answers5