Class: Weka::Core::Attribute

Inherits:
Object
  • Object
show all
Includes:
Weka::Concerns::Persistent
Defined in:
lib/weka/core/attribute.rb

Constant Summary collapse

TYPES = 
%i[numeric nominal string date].freeze

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Weka::Concerns::Persistent

included

Class Method Details

.new_date(name, format) ⇒ Object 



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# File 'lib/weka/core/attribute.rb', line 21

def new_date(name, format)
  new(name.to_s, format.to_s)
end

.new_nominal(name, values) ⇒ Object 



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# File 'lib/weka/core/attribute.rb', line 17

def new_nominal(name, values)
  new(name.to_s, Array(values).map(&:to_s))
end

.new_numeric(name) ⇒ Object 



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# File 'lib/weka/core/attribute.rb', line 13

def new_numeric(name)
  new(name.to_s)
end

.new_string(name) ⇒ Object

Creates a new Attribute instance of type string.

The java class defines the same constructor: Attribute(java.lang.String, java.util.List<java.lang.String>) for nominal and string attributes and handles the type internally based on the second argument.

In Java you would write following code to create a string Attribute:

Attribute attribute = new Attribute("name", (FastVector) null);

When we use a similar approach in JRuby:

attribute = Attribute.new('name', nil)

then a Java::JavaLang::NullPointerException is thrown.

Thus, we use refelection here and call the contructor explicitly, see github.com/jruby/jruby/wiki/CallingJavaFromJRuby#constructors

The object returned from Java constructor only has class Java::JavaObject so we need to cast it to the proper class

See also: stackoverflow.com/questions/1792495/casting-objects-in-jruby



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# File 'lib/weka/core/attribute.rb', line 48

def new_string(name)
  constructor = Attribute.java_class.declared_constructor(
    java.lang.String,
    java.util.List
  )

  constructor.new_instance(name.to_s, nil).to_java(Attribute)
end

Instance Method Details

#internal_value_of(value) ⇒ Object

The order of the if statements is important here, because a date is also a numeric.



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# File 'lib/weka/core/attribute.rb', line 73

def internal_value_of(value)
  return value                      if value.respond_to?(:nan?) && value.nan?
  return Float::NAN                 if [nil, '?'].include?(value)
  return parse_date(value.to_s)     if date?
  return value.to_f                 if numeric?
  return index_of_value(value.to_s) if nominal? || string?
end

#type ⇒ Object

Returns the string representation of the attribute’s type. Overwrites the weka.core.Attribute type Java method, which returns an integer representation of the type based on the defined type constants.



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# File 'lib/weka/core/attribute.rb', line 66

def type
  self.class.type_to_string(self)
end

#values ⇒ Object 



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# File 'lib/weka/core/attribute.rb', line 58

def values
  enumerate_values.to_a
end