Module: ComputationsHelper

Defined in:
lib/sapis/computations_helper.rb

Overview

<computations_helper.rb> - Part of Sav’s APIs. Copyright © 2011 Saverio Miroddi

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <www.gnu.org/licenses/>.

Constant Summary collapse

SMOOTHING_DATA = 
{
  5 => [35.0,  [-3, 12, 17, 12, -3]],
  7 => [21.0,  [-2, 3, 6, 7, 6, 3, -2]],
  9 => [231.0, [-21, 14, 39, 54, 59, 54, 39, 14, -21]],
}

Class Method Summary collapse

Class Method Details

.compute_smoothed_point(buffer, coefficients, h) ⇒ Object 



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# File 'lib/sapis/computations_helper.rb', line 85

def self.compute_smoothed_point(buffer, coefficients, h)
  sum = buffer.zip(coefficients).inject(0) do |current_sum, (value, coefficient)|
    current_sum + value * coefficient
  end

  sum / h
end

.convert_to_incremental_values!(source_values) ⇒ Object

Covnerts to incremental values.

Modifies the original data.

Example:

[ 1, 0, -1, 1 ]

becomes:

[ 1, 1, 0,  1 ]



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# File 'lib/sapis/computations_helper.rb', line 31

def self.convert_to_incremental_values!(source_values)
  current_sum = 0

  source_values.map! do |value|
    if value
      current_sum += value
      current_sum
    end
  end
end

.smooth_line!(values, coefficients_number) ⇒ Object

Reference: stackoverflow.com/questions/4388911/how-can-i-draw-smoothed-rounded-curved-line-graphs-c

Optimized for readability :-)



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# File 'lib/sapis/computations_helper.rb', line 52

def self.smooth_line!(values, coefficients_number)
  h, coefficients = SMOOTHING_DATA[coefficients_number] || raise('Wrong number of coefficients')

  raise "Smoothing needs at least #{coefficients.size} values" if values.compact.size < coefficients.size

  buffer_middle_position = (coefficients.size + 1) / 2 - 1        # 0-based

  non_empty_positions = []
  original_values     = values.clone

  # The complexity is caused by the presence of nil values.
  # We cycle the array, and fill the buffer with the position of each non-null value encountered.
  # When the buffer is ready, we compute the smoothed value and set it, and remove the first entry
  # from the buffer.
  #
  values.each_with_index do |value, current_position|
    non_empty_positions << current_position if value

    next if non_empty_positions.size < coefficients.size

    buffer             = non_empty_positions.map { |non_empty_position| original_values[non_empty_position] }
    modifying_position = non_empty_positions[buffer_middle_position]

    values[modifying_position] = compute_smoothed_point(buffer, coefficients, h)

    non_empty_positions.shift
  end

  nil
end