Class: Array

Inherits:
Object show all
Defined in:
lib/epitools/permutations.rb,
lib/epitools/core_ext/array.rb

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.matrix(height, width, initial_value = nil) ⇒ Object

Create a 2D matrix out of arrays


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# File 'lib/epitools/core_ext/array.rb', line 196

def self.matrix(height, width, initial_value=nil)
  if block_given?
    height.times.map do |row|
      width.times.map do |col|
        yield(row, col)
      end
    end
  else
    height.times.map do
      [initial_value] * width
    end
  end
end

Instance Method Details

#*(other) ⇒ Object

Overridden multiplication operator. Now lets you multiply the Array by another Array or Enumerable.

Array * Integer == a new array with <Integer> copies of itself inside Array * String == a new string containing the elements, joined by the <String> Array * or Enumerable == the cross product (aka. cartesian product) of both arrays


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# File 'lib/epitools/permutations.rb', line 15

def *(other)
  if other.is_a? Array
    # cross-product
    result = []
    (0...self.size).each do |a|
      (0...other.size).each do |b|
        result << [self[a], other[b]]
      end
    end
    result
  else
    send(:mult, other)
  end
end

#**(n) ⇒ Object

Multiply the array by itself `n` times.


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# File 'lib/epitools/permutations.rb', line 33

def **(exponent)
  ([self] * exponent).foldl(:*)
end

#/(pieces) ⇒ Object

Divide the array into n pieces.


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# File 'lib/epitools/core_ext/array.rb', line 133

def / pieces
  piece_size = (size.to_f / pieces).ceil
  each_slice(piece_size).to_a
end

#^(other) ⇒ Object

XOR operator


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# File 'lib/epitools/core_ext/array.rb', line 96

def ^(other)
  (self | other) - (self & other)
end

#all_pairs(reflexive = false) ⇒ Object


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# File 'lib/epitools/permutations.rb', line 37

def all_pairs(reflexive=false)
  (0...size).each do |a|
    start = reflexive ? a : a+1
    (start...size).each do |b|
      yield self[a], self[b]
    end
  end
end

#column(n) ⇒ Object Also known as: col

Return column n of a 2D array


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# File 'lib/epitools/core_ext/array.rb', line 188

def column(n)
  columns[n]&.rtrim!
end

#columnsObject Also known as: cols


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# File 'lib/epitools/core_ext/array.rb', line 171

def columns
  cols = transpose_with_padding
  cols.each &:rtrim!
  cols
end

#histogram(n_buckets = 10, options = {}) ⇒ Object

Takes an array of numbers, puts them into equal-sized buckets, and counts the buckets (aka. A Histogram!)

Examples:

[1,2,3,4,5,6,7,8,9].histogram(3) #=> [3,3,3]
[1,2,3,4,5,6,7,8,9].histogram(2) #=> [4,5]
[1,2,3,4,5,6,7,8,9].histogram(2, ranges: true)
   #=> {
         1.0...5.0 => 4,
         5.0...9.0 => 5
       }

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# File 'lib/epitools/core_ext/array.rb', line 259

def histogram(n_buckets=10, options={})

  use_ranges = options[:ranges] || options[:hash]

  min_val     = min
  max_val     = max
  range       = (max_val - min_val)
  bucket_size = range.to_f / n_buckets
  buckets     = [0]*n_buckets

  # p [range, bucket_size, buckets, min_val, max_val]

  each do |e|
    bucket = (e - min_val) / bucket_size
    bucket = n_buckets - 1 if bucket >= n_buckets
    # p [:e, e, :bucket, bucket]
    buckets[bucket] += 1
  end

  if use_ranges
    ranges = (0...n_buckets).map do |n|
      offset = n*bucket_size
      (min_val + offset) ... (min_val + offset + bucket_size)
    end
    Hash[ ranges.zip(buckets) ]
  else
    buckets
  end

end

#meanObject Also known as: average

Find the statistical mean


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# File 'lib/epitools/core_ext/array.rb', line 73

def mean
  sum / size.to_f
end

#medianObject

Find the statistical median (middle value in the sorted dataset)


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# File 'lib/epitools/core_ext/array.rb', line 81

def median
  sort.middle
end

#middleObject

Pick the middle element


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# File 'lib/epitools/core_ext/array.rb', line 66

def middle
  self[(size-1) / 2]
end

#modeObject

Find the statistical “mode” (most frequently occurring value)


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# File 'lib/epitools/core_ext/array.rb', line 89

def mode
  counts.max_by { |k,v| v }.first
end

#multObject


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# File 'lib/epitools/permutations.rb', line 5

alias_method :mult, :"*

#remove_if(&block) ⇒ Object

Removes the elements from the array for which the block evaluates to true. In addition, return the removed elements.

For example, if you wanted to split an array into evens and odds:

nums = [1,2,3,4,5,6,7,8,9,10,11,12]
even = nums.remove_if { |n| n.even? }   # remove all even numbers from the "nums" array and return them
odd  = nums                             # "nums" now only contains odd numbers

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# File 'lib/epitools/core_ext/array.rb', line 32

def remove_if(&block)
  removed = []

  delete_if do |x|
    if yield(x)
      removed << x
      true
    else
      false
    end
  end

  removed
end

#row(n) ⇒ Object

Return row n of a 2D array


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# File 'lib/epitools/core_ext/array.rb', line 181

def row(n)
  rows[n]
end

#rowsObject

Pseudo-matrix methods


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# File 'lib/epitools/core_ext/array.rb', line 167

def rows
  self
end

#rpad(target_width) ⇒ Object

Return a copy of this array which has been extended to target_width by adding nils to the end (right side)


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# File 'lib/epitools/core_ext/array.rb', line 229

def rpad(target_width)
  dup.rpad!(target_width)
end

#rpad!(target_width) ⇒ Object

Extend the array the target_width by adding nils to the end (right side)


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# File 'lib/epitools/core_ext/array.rb', line 219

def rpad!(target_width)
  if target_width > size and target_width > 0
    self[target_width-1] = nil
  end
  self
end

#rtrim(element = nil) ⇒ Object

Like `rtrim!`, but returns a trimmed copy of the array


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# File 'lib/epitools/core_ext/array.rb', line 159

def rtrim(element=nil)
  dup.rtrim!(element)
end

#rtrim!(element = nil) ⇒ Object

Remove instances of “element” from the end of the array (using `Array#pop`)


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# File 'lib/epitools/core_ext/array.rb', line 151

def rtrim!(element=nil)
  pop while last == element
  self
end

#rzip(other) ⇒ Object

see: Enumerable#rzip


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# File 'lib/epitools/core_ext/array.rb', line 50

def rzip(other)
  super.to_a
  # reverse_each.zip(other.reverse_each).reverse_each.to_a
  # reverse.zip(other.reverse).reverse # That's a lotta reverses!
end

#sample(n = 1) ⇒ Object Also known as: pick


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# File 'lib/epitools/core_ext/array.rb', line 113

def sample(n=1)
  return self[rand sz] if n == 1

  sz      = size
  indices = []

  loop do
    indices += (0..n*1.2).map { rand sz }
    indices.uniq
    break if indices.size >= n
  end

  values_at(*indices[0...n])
end

#shuffleObject


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# File 'lib/epitools/core_ext/array.rb', line 104

def shuffle
  sort_by { rand }
end

#split_at(*args, &block) ⇒ Object

See: Enumerable#split_at


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# File 'lib/epitools/core_ext/array.rb', line 59

def split_at(*args, &block)
  super.to_a
end

#squashObject

flatten.compact.uniq


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# File 'lib/epitools/core_ext/array.rb', line 14

def squash
  flatten.compact.uniq
end

#to_hObject


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# File 'lib/epitools/core_ext/array.rb', line 237

def to_h
  if self.first.is_a? Array
    Hash[self]
  else
    Hash[*self]
  end
end

#transpose_with_paddingObject

Transpose an array that could have rows of uneven length


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# File 'lib/epitools/core_ext/array.rb', line 143

def transpose_with_padding
  max_width = map(&:size).max
  map { |row| row.rpad(max_width) }.transpose
end