method

fit_logarithmic

v2_1_10 - Show latest stable - Class: MiniTest::Unit::TestCase

fit_logarithmic(xs, ys)

public

To fit a functional form: y = a + b*ln(x).

Takes x and y values and returns [a, b, r^2].

See: http://mathworld.wolfram.com/LeastSquaresFittingLogarithmic.html

# File lib/minitest/benchmark.rb, line 265
    def fit_logarithmic xs, ys
      n     = xs.size
      xys   = xs.zip(ys)
      slnx2 = sigma(xys) { |x,y| Math.log(x) ** 2 }
      slnx  = sigma(xys) { |x,y| Math.log(x)      }
      sylnx = sigma(xys) { |x,y| y * Math.log(x)  }
      sy    = sigma(xys) { |x,y| y                }

      c = n * slnx2 - slnx ** 2
      b = ( n * sylnx - sy * slnx ) / c
      a = (sy - b * slnx) / n

      return a, b, fit_error(xys) { |x| a + b * Math.log(x) }
    end

fit_logarithmic

Related methods