Class: Rumale::Preprocessing::MinMaxScaler

Inherits:
Base::Estimator show all
Includes:
Base::Transformer
Defined in:
rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb

Overview

Normalize samples by scaling each feature to a given range.

Examples:

require 'rumale/preprocessing/min_max_scaler'

normalizer = Rumale::Preprocessing::MinMaxScaler.new(feature_range: [0.0, 1.0])
new_training_samples = normalizer.fit_transform(training_samples)
new_testing_samples = normalizer.transform(testing_samples)

Instance Attribute Summary collapse

Attributes inherited from Base::Estimator

#params

Instance Method Summary collapse

Constructor Details

#initialize(feature_range: [0.0, 1.0]) ⇒ MinMaxScaler

Creates a new normalizer for scaling each feature to a given range.

Parameters:

  • feature_range (Array<Float>) (defaults to: [0.0, 1.0]) —

    The desired range of samples.



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# File 'rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb', line 32

def initialize(feature_range: [0.0, 1.0])
  super()
  @params = { feature_range: feature_range }
end

Instance Attribute Details

#max_vec ⇒ Numo::DFloat (readonly)

Return the vector consists of the maximum value for each feature.

Returns:

  • (Numo::DFloat) —

    (shape: [n_features])



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# File 'rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb', line 27

def max_vec
  @max_vec
end

#min_vec ⇒ Numo::DFloat (readonly)

Return the vector consists of the minimum value for each feature.

Returns:

  • (Numo::DFloat) —

    (shape: [n_features])



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# File 'rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb', line 23

def min_vec
  @min_vec
end

Instance Method Details

#fit(x) ⇒ MinMaxScaler

Calculate the minimum and maximum value of each feature for scaling.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The samples to calculate the minimum and maximum values.

Returns:



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# File 'rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb', line 43

def fit(x, _y = nil)
  x = ::Rumale::Validation.check_convert_sample_array(x)

  @min_vec = x.min(0)
  @max_vec = x.max(0)
  self
end

#fit_transform(x) ⇒ Numo::DFloat

Calculate the minimum and maximum values, and then normalize samples to feature_range.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The samples to calculate the minimum and maximum values.

Returns:

  • (Numo::DFloat) —

    The scaled samples.



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# File 'rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb', line 57

def fit_transform(x, _y = nil)
  x = ::Rumale::Validation.check_convert_sample_array(x)

  fit(x).transform(x)
end

#transform(x) ⇒ Numo::DFloat

Perform scaling the given samples according to feature_range.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The samples to be scaled.

Returns:

  • (Numo::DFloat) —

    The scaled samples.



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# File 'rumale-preprocessing/lib/rumale/preprocessing/min_max_scaler.rb', line 67

def transform(x)
  x = ::Rumale::Validation.check_convert_sample_array(x)

  n_samples, = x.shape
  dif_vec = @max_vec - @min_vec
  dif_vec[dif_vec.eq(0)] = 1.0
  nx = (x - @min_vec.tile(n_samples, 1)) / dif_vec.tile(n_samples, 1)
  nx * (@params[:feature_range][1] - @params[:feature_range][0]) + @params[:feature_range][0]
end