cov.rb

#!/usr/bin/env ruby
require 'Matrix'

class B
  attr_accessor :points
  attr_reader :average

  def initialize
    @points = []
    @average = [0, 0, 0]
  end

  def add_point(coord)
    @points << coord
  end

  def calculate_average
    @points.each do |point|
      @average[0] += point[0]
      @average[1] += point[1]
      @average[2] += point[2]
    end

    @average = @average.map { |item| item / @points.size }
  end

  def cov(i, j)
    (@points.inject(0) do |acc, point|
      acc += (point[i] - @average[i]) * (point[j] - @average[j])
    end / (@points.size - 1)).round(4)
  end
end

b = B.new
b.add_point [50.0, 50.0, 50.0]
b.add_point [32.0, 34.0, 25.0]
b.add_point [25.0, 30.0, 30.0]
b.add_point [35.0, 30.0, 30.0]
b.calculate_average

puts "AVERAGE: #{b.average}"

k = []
3.times do |i|
  k << []
  3.times do |j|
    k[i] << b.cov(i,j) 
  end
end

c = Matrix.rows(k)
p c

v, d, v_inv = c.eigensystem

p v
p d
p v_inv

puts '---'
puts '---'

p v_inv.row(0)
p c * v_inv.row(0)

p d.element(0,0) * v_inv.row(0)

if false
k.each { |row| p row }

print '{'
k.each do |row|
  print '{'
  out = []
  row.each do |item|
    out << item
  end
  print out.join(',')
  print '},'
end
print '}'
end