I have a set of data that is an array of hashes, with each hash representing one record of data:
data = [
{
:id => "12345",
:bucket_1_rank => "2",
:bucket_1_count => "12",
:bucket_2_rank => "7",
:bucket_2_count => "25"
},
{
:id => "45678",
:bucket_1_rank => "2",
:bucket_1_count => "15",
:bucket_2_rank => "9",
:bucket_2_count => "68"
},
{
:id => "78901",
:bucket_1_rank => "5",
:bucket_1_count => "36"
}
]
The ranks values are always between 1 and 10.
What I am trying to do is select each of the possible values for the rank fields (the :bucket_1_rank and :bucket_2_rank fields) as keys in my final resultset, and the values for each key will be an array of all the values in its associated :bucket_count field. So, for the data above, the final resulting structure I have in mind is something like:
bucket 1:
{"2" => ["12", "15"], "5" => ["36"]}
bucket 2:
{"7" => ["25"], "9" => ["68"]}
I can do this working under the assumption that the field names stay the same, or through hard coding the field/key names, or just using group_by for the fields I need, but my problem is that I work with a different data set each month where the rank fields are named slightly differently depending on the project specs, and I want to identify the names for the count and rank fields dynamically as opposed to hard coding the field names.
I wrote two quick helpers get_ranks and get_buckets that use regex to return an array of fieldnames that are either ranks or count fields, since these fields will always have the literal string "_rank" or "_count" in their names:
ranks = get_ranks
counts = get_counts
results = Hash.new{|h,k| h[k] = []}
data.each do |i|
ranks.each do |r|
unless i[r].nil?
counts.each do |c|
results[i[r]] << i[c]
end
end
end
end
p results
This seems to be close, but feels awkward, and it seems to me there has to be a better way to iterate through this data set. Since I haven't worked on this project using Ruby I'd use this as an opportunity to improve my understanding iterating through arrays of hashes, populating a hash with arrays as values, etc. Any resources/suggestions would be much appreciated.
You could shorten it to:
result = Hash.new{|h,k| h[k] = Hash.new{|h2,k2| h2[k2] = []}}
data.each do |hsh|
hsh.each do |key, value|
result[$1][value] << hsh["#{$1}_count".to_sym] if key =~ /(.*)_rank$/
end
end
puts result
#=> {"bucket_1"=>{"2"=>["12", "15"], "5"=>["36"]}, "bucket_2"=>{"7"=>["25"], "9"=>["68"]}}
Though this is assuming that :bucket_2_item_count is actually supposed to be :bucket_2_count.
Related
i have a matrix like this
[
["name", "company1", "company2", "company3"],
["hr_admin", "Tom", "Joane", "Kris"],
["manager", "Philip", "Daemon", "Kristy"]
]
How can I convert into this data structure?
{
"company1" => {
"hr_admin"=> "Tom",
"manager" => "Philip"
},
"Company2" => {
"hr_admin"=> "Joane",
"manager" => "Daemon"
},
"company3" => {
"hr_admin"=> "Kris",
"manager" => "Kristy"
}
}
I have tried approach like taking out the first row of matrix (header) and zipping the rest o
f the matrix to change their position. It worked to some extent but it doesnt looks very good. So I am turning up here for help.
matrix[0][1...matrix[0].length].each_with_index.map do |x,i|
values = matrix[1..matrix.length].map do |x|
[x[0], x[i+1]]
end.to_h
[x, values]
end.to_h
matrix[0].length and matrix.length could be omittable depending on ruby version.
First you take all elements of first row but first.
then you map them with index to e.g. [["hr_admin", "Tom"],["manager", "Phil"]] using the index
then you call to_h on every element and on whole array.
arr = [
["name", "company1", "company2", "company3"],
["hr_admin", "Tom", "Joane", "Kris"],
["manager", "Philip", "Daemon", "Kristy"]
]
Each key-value pair of the hash to be constructed is formed from the "columns" of arr. It therefore is convenient to compute the transpose of arr:
(_, *positions), *by_company = arr.transpose
#=> [["name", "hr_admin", "manager"],
# ["company1", "Tom", "Philip"],
# ["company2", "Joane", "Daemon"],
# ["company3", "Kris", "Kristy"]]
I made use of Ruby's array decomposition (a.k.a array destructuring) feature (see this blog for elabortion) to assign different parts of the inverse of arr to variables. Those values are as follows1.
_ #=> "name"
positions
#=> ["hr_admin", "manager"]
by_company
#=> [["company1", "Tom", "Philip"],
# ["company2", "Joane", "Daemon"],
# ["company3", "Kris", "Kristy"]]
It is now a simple matter to form the desired hash. Once again I will use array decomposition to advantage.
by_company.each_with_object({}) do |(company_name, *employees),h|
h[company_name] = positions.zip(employees).to_h
end
#=> {"company1"=>{"hr_admin"=>"Tom", "manager"=>"Philip"},
# "company2"=>{"hr_admin"=>"Joane", "manager"=>"Daemon"},
# "company3"=>{"hr_admin"=>"Kris", "manager"=>"Kristy"}}
When, for example,
company_name, *employees = ["company1", "Tom", "Philip"]
company_name
#=> "company1"
employees
#=> ["Tom", "Philip"]
so
h[company_name] = positions.zip(employees).to_h
h["company1"] = ["hr_admin", "manager"].zip(["Tom", "Philip"]).to_h
= [["hr_admin", "Tom"], ["manager", "Philip"]].to_h
= {"hr_admin"=>"Tom", "manager"=>"Philip"}
Note that these calculations do not depend on the numbers of rows or columns of arr.
1. As is common practice, I used the special variable _ to signal to the reader that its value is not used in subsequent calculations.
I'm having some trouble iterating through a series of nested hashes, and I think its because the inner hashes are named with strings. Unfortunately, I cannot simply change these names. Here is a generic hash of the kind that I am working with:
hash =
"name" => {
"stuff" => "value",
"key" => "value", },
"name" => {
"stuff" => "value",
"key" => "value", },
I'm trying to write a program that will print the fields labelled as "name" as well the values, within, when called by the names of their keys. Right now, I am stuck with
hash.each do |key, value|
puts key
key.each do |stuff, info|
puts info if category == "stuff"
end
end
but this gives the error that each is not a recognized method for the key, which is, I think, because the computer is treating it as a string due to its naming. Does anyone have any ideas how I can proceed from here (without changing the names of the keys)?
As #meager says - the sub-hash is in the value. Try this
hash.each do |key, sub_hash|
puts key
sub_hash.each do |category, info|
puts info if category == "stuff"
end
end
What you have is an array of hashes, and not a Hash:
arr = [
{"name" => {"stuff" => "value","key" => "value" }},
{"name" => {"stuff" => "value","key" => "value" }},
{"noname" => {}}
]
arr.each do |hash|
name = hash["name"]
puts name["stuff"] if name
end
I want to create an array of hashes in ruby as:
arr[0]
"name": abc
"mobile_num" :9898989898
"email" :abc#xyz.com
arr[1]
"name": xyz
"mobile_num" :9698989898
"email" :abcd#xyz.com
I have seen hash and array documentation. In all I found, I have to do something
like
c = {}
c["name"] = "abc"
c["mobile_num"] = 9898989898
c["email"] = "abc#xyz.com"
arr << c
Iterating as in above statements in loop allows me to fill arr. I actually rowofrows with one row like ["abc",9898989898,"abc#xyz.com"]. Is there any better way to do this?
Assuming what you mean by "rowofrows" is an array of arrays, heres a solution to what I think you're trying to accomplish:
array_of_arrays = [["abc",9898989898,"abc#xyz.com"], ["def",9898989898,"def#xyz.com"]]
array_of_hashes = []
array_of_arrays.each { |record| array_of_hashes << {'name' => record[0], 'number' => record[1].to_i, 'email' => record[2]} }
p array_of_hashes
Will output your array of hashes:
[{"name"=>"abc", "number"=>9898989898, "email"=>"abc#xyz.com"}, {"name"=>"def", "number"=>9898989898, "email"=>"def#xyz.com"}]
you can first define the array as
array = []
then you can define the hashes one by one as following and push them in the array.
hash1 = {:name => "mark" ,:age => 25}
and then do
array.push(hash1)
this will insert the hash into the array . Similarly you can push more hashes to create an array of hashes.
You could also do it directly within the push method like this:
First define your array:
#shopping_list_items = []
And add a new item to your list:
#shopping_list_items.push(description: "Apples", amount: 3)
Which will give you something like this:
=> [{:description=>"Apples", :amount=>3}]
Given two hashes, I'm trying to replace a value in the first hash for a key that the second hash also has. To be specific, I have these two hashes:
data = {
"study" => "Lucid Study",
"name" => "Lucid Plan",
"studyWillBe" => "Combination"
}
conditions = { "study" => "((current))" }
I want data to have its "study" key updated since conditions has that key. I want data to end up like this:
data = {
"study" => "((current))",
"name" => "Lucid Plan",
"studyWillBe" => "Combination"
}
I got this far:
data = Hash[data.map {|k, v| [conditions[k] || k, v] }]
but that's not quite doing the trick. Can anyone point me in the right direction?
You can do this
data.each {|k, v| data[k] = conditions[k] if conditions[k]}
It's called merge.
data = {"study"=>"Lucid Study", "name"=>"Lucid Plan", "studyWillBe"=>"Combination"}
conditions = {"study"=>"((current))"}
data.merge(conditions)
#{"study"=>"((current))", "name"=>"Lucid Plan", "studyWillBe"=>"Combination"}
The method merge can take a block where you can make some specific operation not only assign new value
data.merge(conditions) do |key, oldvalue, newvalue|
newvalue
end
=> {"study"=>"((current))", "name"=>"Lucid Plan", "studyWillBe"=>"Combination"}
For the sake of convenience I am trying to assign multiple values to a hash key in Ruby. Here's the code so far
myhash = { :name => ["Tom" , "Dick" , "Harry"] }
Looping through the hash gives a concatenated string of the 3 values
Output:
name : TomDickHarry
Required Output:
:name => "Tom" , :name => "Dick" , :name => "Harry"
What code must I write to get the required output?
myhash.each_pair {|k,v| v.each {|n| puts "#{k} => #{n}"}}
#name => Tom
#name => Dick
#name => Harry
The output format is not exactly what you need, but I think you get the idea.
The answers from Rohith and pierr are fine in this case. However, if this is something you're going to make extensive use of it's worth knowing that the data structure which behaves like a Hash but allows multiple values for a key is usually referred to as a multimap. There are a couple of implementations of this for Ruby including this one.
You've created a hash with the symbol name as the key and an array with three elements as the value, so you'll need to iterate through myhash[:name] to get the individual array elements.
re: the issue of iterating over selective keys. Try using reject with the condition inverted instead of using select.
e.g. given:
{:name=>["Tom", "Dick", "Harry"], :keep=>[4, 5, 6], :discard=>[1, 2, 3]}
where we want :name and :keep but not :discard
with select:
myhash.select { |k, v| [:name, :keep].include?(k) }
=> [[:name, ["Tom", "Dick", "Harry"]], [:keep, [4, 5, 6]]]
The result is a list of pairs.
but with reject:
myhash.reject { |k, v| ![:name, :keep].include?(k) }
=> {:name=>["Tom", "Dick", "Harry"], :keep=>[4, 5, 6]}
The result is a Hash with only the entries you want.
This can then be combined with pierr's answer:
hash_to_use = myhash.reject { |k, v| ![:name, :keep].include?(k) }
hash_to_use.each_pair {|k,v| v.each {|n| puts "#{k} => #{n}"}}