Class: Musicality::Function::Sigmoid

Inherits:
Musicality::Function show all
Defined in:
lib/musicality/notation/util/function.rb

Constant Summary collapse

SIGM_DOMAIN =

def self.inv_sigm y

-Math::log((1-y)/y.to_f)

end

-5..5
SIGM_RANGE = 
Sigmoid.sigm(SIGM_DOMAIN.first)..Sigmoid.sigm(SIGM_DOMAIN.last)
SIGM_SPAN = 
SIGM_RANGE.last - SIGM_RANGE.first

Instance Attribute Summary collapse

Attributes inherited from Musicality::Function

#domain

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Musicality::Function

#at, #sample, transform_domains

Constructor Details

#initialize(p0, p1) ⇒ Sigmoid

Returns a new instance of Sigmoid.



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# File 'lib/musicality/notation/util/function.rb', line 87

def initialize p0, p1
  @y0, y1 = p0[1], p1[1]
  @dy = y1 - @y0
  @external_domain = p0[0]..p1[0]

  super() do |x|
    x_ = Function.transform_domains(@external_domain, SIGM_DOMAIN, x)
    y_ = (Sigmoid.sigm(x_) - SIGM_RANGE.first) / SIGM_SPAN
    @y0 + y_ * @dy
  end
end

Instance Attribute Details

#dy ⇒ Object (readonly)

Returns the value of attribute dy.



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# File 'lib/musicality/notation/util/function.rb', line 86

def dy
  @dy
end

#y0 ⇒ Object (readonly)

Returns the value of attribute y0.



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# File 'lib/musicality/notation/util/function.rb', line 86

def y0
  @y0
end

Class Method Details

.find_y0(domain, pt, y1) ⇒ Object

Given a domain, an xy-point in that domain, and the y-value at the end of the domain, find the y-value at the start of the domain, assuming the the function is sigmoid.



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# File 'lib/musicality/notation/util/function.rb', line 109

def self.find_y0 domain, pt, y1
  x,y = pt
  x_ = Function.transform_domains(domain, SIGM_DOMAIN, x)
  y_ = (sigm(x_) - SIGM_RANGE.first) / SIGM_SPAN
  return Function::Linear.new([y_,y],[1,y1]).at(0)
end

.sigm(x) ⇒ Object 



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# File 'lib/musicality/notation/util/function.rb', line 74

def self.sigm x
  1.0 / (1 + Math::exp(-x))
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/musicality/notation/util/function.rb', line 116

def ==(other)
  super(other) && @y0 == other.y0 && @dy == other.dy
end