I am new to ruby on rails and trying to make a multidimensional hash from different arrays.
persons= [person1, person2, person3, person4]
projects= [project1, project2, project3]
issues= [1000, 10001, 1002, 1003, 1004,1005,1006,1007,1008,1009,1010]
issuetime = [1, 2 , 3, 4, 5]
I want a Hash like this:
hash = {person 1 =>{project1 => {1000, 1001, 1002 => {1,2,3}}}, person2 =>{project1 => {1003, 1004, 1005 => {3,4,5}}}}
I tried:
hash= {}
persons.each_with_index do [person,i]
if hash.has_key?(person)
hash[person] << projects[i]
else
hash[person] = [projects[i]]
end
end
This is working but it shows me only:
hash = {{person 1 =>{project1}}, {person2=>{project2}}}.
I want a multidimensional Hash if this is possible. I dont know how to access the next key + value to build a multidimensional hash.
Thanks for your help!
persons = ['person1', 'person2', 'person3']
projects = ['project1', 'project2', 'project3']
issues = [1000, 10001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010]
issuetimes = [1, 2 ,3, 4, 5, 6, 7, 8, 9]
persons.each_with_object({}).with_index do |(person, hsh), index|
hsh[person] = {
projects[index] => {
issues.slice!(0, 3) => issuetimes.slice!(0, 3)
}
}
end
This will give you. {"person1"=>{"project1"=>{[1000, 10001, 1002]=>[1, 2, 3]}}, "person2"=>{"project2"=>{[1003, 1004, 1005]=>[4, 5, 6]}}, "person3"=>{"project3"=>{[1006, 1007, 1008]=>[7, 8, 9]}}}
A couple of things to note about this question.
{1000, 1001, 1002 => {1,2,3}} is not a valid hash, as it will throw an error. However, you can do the following [1, 2, 3]=>[4, 5, 6]}, so my answer above assumes that is what you want to do.
My solution uses the destructive form of slice!, so note that the issues and issuetimes arrays will be changed from this solution. If you don't want that I would make duplicates of those arrays using the dup method.
On a somewhat related note, you might want to check out zip when it comes to creating hashes from arrays. Hash[persons.zip(projects)] // {"person1"=>"project1", "person2"=>"project2", "person3"=>"project3"}, which is not what you want here, but I thought I would mention it.
Related
Ok so I have an array of 'winner ids' this array represents users who have won in the previous round of a tournament. I then have an array of objects called 'tournament participations', this represents all the users that have participated in the tournament (many to many relationship join table).
For each 'winner id' I want to iterate through the 'tournament participations' array and find the tournament participation with a user_id that matches the 'winner id', then push it into a new array called 'round participations'...
I have tried the code below but I always get returned the original 'winner_ids' array....
#challenges = Challenge.where(tournament_id: #tournament.id)
#winner_ids = #challenges.pluck(:winner_id)
#tournament_participations = #tournament.tournament_participations
#round_participations = []
#round_participations = #winner_ids.each do |winner_id|
#round_participation = #tournament_participations.where(user_id: winner_id)
#round_participations << #round_participation
end
each returns the enumerable it was called on; in this case, #winner_ids.each is returning #winner.ids. You don't need to assign the result of the iteration to #round_participations.
Also, check out the map method.
Use the map method, instead of .each.
The map method can be used to create a new array based on the original array, but with the values modified by the supplied block. See the below example.
In case of each method
irb(main):001:0> arr = [1, 2, 3, 4, 5]
=> [1, 2, 3, 4, 5]
irb(main):002:0> arr.each { |a| print a -= 10, " " }
-9 -8 -7 -6 -5
=> [1, 2, 3, 4, 5]
you can see after iterations it returned the original array. But in the case of map
irb(main):005:0> arr = [1, 2, 3, 4, 5]
=> [1, 2, 3, 4, 5]
irb(main):006:0> arr.map { |a| 2*a }
=> [2, 4, 6, 8, 10]
map can transform the contents of an array, meaning that it can perform an operation on each element in the array.
I have an array of JSON object.
arr = [{'a'=> 1, 'b'=> 2, 'c'=> 3}, {'a'=> 4, 'b'=> 5,'c'=> 6}, {'a'=> 4, 'b'=> 5,'c'=> 6}]
But I want an new array which select 'a' and 'c' attributes only:
new_arr = [{'a'=> 1, 'c'=> 3}, {'a'=> 4,'c'=> 6}, {'a'=> 4,'c'=> 6}]
I try to use map but for 1 attribute only arr.map{|i| i['a']}.
What I am missing or any suggestion?
Make use of slice and pass the attributes you want to select
arr = [{'a'=> 1, 'b'=> 2, 'c'=> 3}, {'a'=> 4, 'b'=> 5,'c'=> 6}, {'a'=> 4, 'b'=> 5,'c'=> 6}]
arr.map{|a| a.slice('a', 'c')}
#=> [{"a"=>1, "c"=>3}, {"a"=>4, "c"=>6}, {"a"=>4, "c"=>6}]
You can use except
new_arr = arr.map{ |e| e.except('b') }
Since, there are already answers describing usage of slice and except, I would provide another way here:
arr.map{|h| {'a' => h['a'], 'c' => h['c'] } }
#=> [{"a"=>1, "c"=>3}, {"a"=>4, "c"=>6}, {"a"=>4, "c"=>6}]
Note that h here is a particular object of the array being iterated inside map, which is a Hash.
Bit more of a code to be typed though. You could use select as well.
OK, so I have this array of arrays. Each array within the larger array is very much the same, ten specific values. If my value at location 3 is a specific value, then I want to iterate through the rest of the remaining arrays within the larger array and see if the first 3 values at locations 0, 1, and 2 match. if they then match, I'd like to delete the original array. I'm having a hard time with it, maybe there is an easy way? I'm sure there is, I'm fairly new to this whole coding stuff =) So much appreciation in advance for your help....
here's where I'm at:
#projectsandtrials.each do |removed|
if removed[3] == ["Not Harvested"]
#arraysforloop = #projectsandtrials.clone
#arraysforloop1 = #arraysforloop.clone.delete(removed)
#arraysforloop1.each do |m|
if (m & [removed[0], removed[1], removed[2]]).any?
#projectsandtrials.delete(removed)
end
end
end
end
Lets look at your situation:
#projectsandtrials.each do |removed|
// some logic, yada yada
#projectsandtrials.delete(removed)
end
You can't just delete stuff out of an array you're iterating through. At least not until you finish iterating through it. What you should be using instead is a filtering method like reject instead of just an each.
So instead of deleting right there, you should just return true when using reject.
I think about it like this when iterating through arrays.
Do I want the array to stay the same size and have the same content?
Use each.
Do I want the array to be the same size, but have different content?
Use map.
Do I want the array to be less than or equal to the current size?
Use select or reject.
Do I want it to end up being a single value?
Use reduce.
Code
def prune(arr, val)
arr.values_at(*(0..arr.size-4).reject { |i| arr[i][3] == val &&
arr[i+1..i+3].transpose[0,3].map(&:uniq).all? { |a| a.size==1 } }.
concat((arr.size-3..arr.size-1).to_a))
end
Example
arr = [ [1,2,3,4,0],
[3,4,5,6,1],
[3,4,5,4,2],
[3,4,5,6,3],
[3,4,5,6,4],
[3,4,0,6,5],
[2,3,5,4,6],
[2,3,5,5,7],
[2,3,5,7,8],
[2,3,5,8,9],
[2,3,5,7,0]
]
Notice that the last values of the elements (arrays) of arr are consecutive. This is to help you identify the elements of prune(arr, 4) (below) that have been dropped.
prune(arr, 4)
# => [[3, 4, 5, 6, 1],
# [3, 4, 5, 4, 2],
# [3, 4, 5, 6, 3],
# [3, 4, 5, 6, 4],
# [3, 4, 0, 6, 5],
# [2, 3, 5, 5, 7],
# [2, 3, 5, 7, 8],
# [2, 3, 5, 8, 9],
# [2, 3, 5, 7, 0]]
Explanation
The arrays at indices 0 and 6 have not been included in array returned.
arr[0] ([1,2,3,4,0]) has not been included because arr[0][3] = val = 4 and arr[1], arr[2] and arr[3] all begin [3,4,5].
arr[6] ([2,3,5,4,6]) has not been included because arr[6][3] = 4 and arr[7], arr[8] and arr[9] all begin [2,3,5].
arr[2] ([3,4,5,5,2]) has been included because, while arr[2][3] = 4, arr[3][0,3], arr[4][0,3] and arr[5][0,3] all not all equal (i.e., arr[5][2] = 0).
Notice that the last three elements of arr will always be included in the array returned.
Now let's examine the calculations. First consider the following.
arr.size
#=> 11
a = (0..arr.size-4).reject { |i| arr[i][3] == val &&
arr[i+1..i+3].transpose[0,3].map(&:uniq).all? { |a| a.size==1 } }
#=> (0..7).reject { |i| arr[i][3] == val &&
arr[i+1..i+3].transpose[0,3].map(&:uniq).all? { |a| a.size==1 } }
#=> [1, 2, 3, 4, 5, 7]
Consider reject's block calculation for i=0 (recall val=4).
arr[i][3] == val && arr[i+1..i+3].transpose[0,3].map(&:uniq).all? {|a| a.size==1 }}
#=> 4 == 4 && arr[1..3].transpose[0,3].map(&:uniq).all? { |a| a.size==1 }
#=> [[3,4,5,6,1],
# [3,4,5,4,2],
# [3,4,5,6,3]].transpose[0,3].map(&:uniq).all? { |a| a.size==1 }
#=> [[3, 3, 3],
# [4, 4, 4],
# [5, 5, 5],
# [6, 4, 6],
# [1, 2, 3]][0,3].map(&:uniq).all? { |a| a.size==1 }
#=> [[3, 3, 3],
# [4, 4, 4],
# [5, 5, 5]].map(&:uniq).all? { |a| a.size==1 }
#=> [[3], [4], [5]].all? { |a| a.size==1 }
#=> true
meaning arr[0] is to be rejected; i.e., not included in the returned array.
The remaining block calculations (for i=1,...,10) are similar.
We have computed
a #=> [1, 2, 3, 4, 5, 7]
which are the indices of all elements of arr except the last 3 that are to be retained. To a we add the indices of the last three elements of arr.
b = a.concat((arr.size-3..arr.size-1).to_a)
#=> a.concat((8..10).to_a)
#=> a.concat([8,9,10])
#=> [1, 2, 3, 4, 5, 7, 8, 9, 10]
Lastly,
arr.values_at(*b)
returns the array given in the example.
Your code snippet seems fine, although there are couple of things to note:
#arraysforloop.clone.delete(removed) removes all the occurences of removed array (not only the first one). E.g. [1,2,3,1].delete(1) would leave you with [2,3]. You could fix it with using an iterator for #projectsandtrials and delete_at method.
delete method returns the same argument you pass to it (or nil if no matches found). So #arraysforloop1 = #arraysforloop.clone.delete(removed) makes your #arraysforloop1 to contain the removed array's elements only! Removing an assignment could save you.
I see no reason to have two cloned arrays, #arraysforloop and #arraysforloop1, as the former one is not used anyhow later. May be we could omit one of them?
#projectsandtrials.delete(removed) leaves you in a strange state, as long as you're iterating the same array right now. This could end up with you missing the right next element after the removed one. Here is a simple snippet to illustrate the behaviour:
> a = [1,2,3]
> a.each{|e, index| puts("element is: #{e}"); a.delete(1);}
element is: 1
element is: 3
As you see, after deleting element 1 the loop moved to element 3 directly, omitting the 2 (as it became the first element in array and algorithm thinks it's been handled already).
One of the possibilities to make it less messy is to split it to a bundle of methods. Here is an option:
def has_searched_element? row
# I leave this method implementation to you
end
def next_rows_contain_three_duplicates?(elements, index)
# I leave this method implementation to you
end
def find_row_ids_to_remove elements
[].tap do |result|
elements.each_with_index do |row, index|
condition = has_searched_element?(row) && next_rows_contain_three_duplicates?(elements, index)
result << index if condition
end
end
end
row_ids_to_remove = find_row_ids_to_remove(#projectsandtrials)
# now remove all the elements at those ids out of #projectsandtrials
I'm coding a plugin in Google Sketchup with ruby and I faced a real problem while trying to permute two arrays that are present in an array all this depending on a user combination.
I have an array of arrays like [["1"],["lol"], ["so"]]
When we have a combination like this <[1,
2, 3] it's fine, it should stay the same : [["1"],["lol"], ["so"]]
But when we have a combination like this [2, 3, 1], the output should be : [["lol"], ["so"], ["1"]]
For [3,1,2] => [["so"], ["1"], ["lol"]]
...etc
EDIT
Sorry guys I forgot for the array I have a bit like : [["1, 2, 3"], ["lol1, lol2, lol3"], ["so1, so2, so3"]] so for the combination [2, 3, 1] the output should be : [["2, 3, 1"], ["lol2, lol3, lol1"], ["so2, so3, so1"]]
Thanks for helping me out.
You could use collect:
array = [["1"],["lol"], ["so"]]
indexes = [2, 1, 3]
indexes.collect {|i| array[i-1]} #=> [["lol"], ["1"], ["so"]]
If you set the indexes to be 0-based you could drop the -1
split and map can be used to turn your strings into values:
"1, 2, 3".split(",").map { |i| i.to_i} # [1, 2, 3]
You can then also split your strings
"lol2, lol3, lol1".split(/, /) #=> ["lol2", "lol3", "lol1"]
You should be able to put that together with the above to get what you want.
indexes = [2, 1, 3]
array = [["1"],["lol"], ["so"]]
result = indexes.map{|index| array[index-1] }
You should also take a look at active_enum
https://github.com/adzap/active_enum
You could do something like:
class YourClassName < ActiveEnum::Base
value [1] => ['1']
value [2] => ['lol']
value [3] => ['so']
end
a = [["1"], ["lol"], ["so"]]
index = [2, 1, 3]
index.collect {|i| a[i - 1]}
This outputs
[["lol"], ["1"], ["so"]]
Lets say I have an array
[0, 132, 432, 342, 234]
What is the easiest way to get rid of the first element? (0)
Use .drop(1).
This has the benefit of returning a new Array with the first element removed, as opposed to using .shift, which returns the removed element, not the Array with the first element removed.
NOTE: It does not affect/mutate the original Array.
a = [0,1,2,3]
a.drop(1)
# => [1, 2, 3]
a
# => [0,1,2,3]
And, additionally, you can drop more than the first element:
[0,1,2,3].drop(2)
=> [2, 3]
[0,1,2,3].drop(3)
=> [3]
Use the shift method on array
>> x = [4,5,6]
=> [4, 5, 6]
>> x.shift
=> 4
>> x
=> [5, 6]
If you want to remove n starting elements you can use x.shift(n)
"pop"ing the first element of an Array is called "shift" ("unshift"
being the operation of adding one element
in front of the array).
[0, 132, 432, 342, 234][1..]
=> [132, 432, 342, 234]
So unlike shift or slice, this returns a new array, keeping the original array untouched (useful for one liners).
This is pretty neat:
head, *tail = [1, 2, 3, 4, 5]
#==> head = 1, tail = [2, 3, 4, 5]
As written in the comments, there's an advantage of not mutating the original list.
or a.delete_at 0
Use shift method
array.shift(n) => Remove first n elements from array
array.shift(1) => Remove first element
https://ruby-doc.org/core-2.2.0/Array.html#method-i-shift
You can use:
a.slice!(0)
slice! generalizes to any index or range.
You can use Array.delete_at(0) method which will delete first element.
x = [2,3,4,11,0]
x.delete_at(0) unless x.empty? # [3,4,11,0]
You can use:
arr - [arr[0]]
or
arr - [arr.shift]
or simply
arr.shift(1)
You can use:
a.delete(a[0])
a.delete_at 0
Both can work