Module: ChrisMath

Includes:
Math
Defined in:
lib/chris_lib/chris_math.rb

Instance Method Summary collapse

Instance Method Details

#bi_gaussian_rand ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 184

def bi_gaussian_rand
  u1 = rand()
  u2 = rand()
  z0 = sqrt(-2*log(u1))*cos(2*PI*u2)
  z1 = sqrt(-2*log(u1))*sin(2*PI*u2)
  [z0,z1]
end

#combinatorial(n, k) ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 228

def combinatorial(n, k)
  #from rosetta code
  (0...k).inject(1) do |m,i| (m * (n - i)) / (i + 1) end
end

#combinatorial_distribution(n, r, p) ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 209

def combinatorial_distribution(n,r,p)
  # probability that r out n or greater hits with the 
  # probability of one hit is p.
  if r <= n && r >= 0
  sum = 0
  (r..n).each do |k|
    sum += combinatorial(n,k)*(p)**(k)*(1-p)**(n - k)
  end
  sum
  else
    raise 'Error, #{r} must be >= 0  and <= #{n}'
  end
end

#factorial(n) ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 223

def factorial(n)
  #from rosetta code
  (1..n).inject {|prod, i| prod * i}
end

#gaussian_array(n = 1) ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 176

def gaussian_array(n = 1)
  (1..n).map do
    u1 = rand()
    u2 = rand()
    sqrt(-2*log(u1))*cos(2*PI*u2)
  end
end

#gaussian_rand(mean, std) ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 192

def gaussian_rand(mean,std)
  u1 = rand()
  u2 = rand()
  z0 = sqrt(-2*log(u1))*cos(2*PI*u2)
  z0*std + mean
end

#std(values) ⇒ Object 



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# File 'lib/chris_lib/chris_math.rb', line 200

def std(values)
  n = values.length
  raise 'n = #{n} but must be greater than 1' if n < 2
  m = mean(values)
  sum = values.inject { |s,v| s + (v**2 - m**2)}
  sqrt(sum.to_f/(n - 1))
end