class LibSVMLoader

LibSVMLoader loads (and dumps) dataset file with the libsvm file format.

Constants

VERSION

Public Class Methods

dump_libsvm_file(data, labels, filename, zero_based: false) click to toggle source

Dump the dataset with the libsvm file format.

@param data [Array] (n_samples x n_features) matrix consisting of feature vectors. @param labels [Array] (n_samples) vector consisting of labels or target values. @param filename [String] Path to the output libsvm file. @param zero_based [Boolean] Whether the column index starts from 0 (true) or 1 (false).

# File lib/libsvmloader.rb, line 40
def dump_libsvm_file(data, labels, filename, zero_based: false)
  n_samples = data.size < labels.size ? data.size : labels.size
  label_format = detect_format(labels[0])
  value_format = detect_format(data.flatten[0])
  File.open(filename, 'w') do |file|
    n_samples.times { |n| file.puts(dump_libsvm_line(labels[n], data[n], label_format, value_format, zero_based)) }
  end
end

load_libsvm_file(filename, zero_based: false, label_dtype: 'int', value_dtype: 'float') click to toggle source

Load a dataset with the libsvm file format.

@param filename [String] Path to a dataset file. @param zero_based [Boolean] Whether the column index starts from 0 (true) or 1 (false). @param label_dtype [String] Data type of labels or target values ('int', 'float', 'complex'). @param value_dtype [String] Data type of feature vectors ('int', 'float', 'complex').

@return [Array<Array>]

Returns array containing the (n_samples x n_features) matrix for feature vectors
and (n_samples) vector for labels or target values.

# File lib/libsvmloader.rb, line 19
def load_libsvm_file(filename, zero_based: false, label_dtype: 'int', value_dtype: 'float')
  labels = []
  ftvecs = []
  maxids = []
  label_class = parse_dtype(label_dtype)
  value_class = parse_dtype(value_dtype)
  CSV.foreach(filename, col_sep: "\s", headers: false) do |row|
    label, ftvec, maxid = parse_libsvm_row(row, zero_based, label_class, value_class)
    labels.push(label)
    ftvecs.push(ftvec)
    maxids.push(maxid)
  end
  [convert_to_matrix(ftvecs, maxids.max + 1, value_class), labels]
end

Private Class Methods

convert_to_matrix(data, n_features, value_type) click to toggle source

# File lib/libsvmloader.rb, line 91
def convert_to_matrix(data, n_features, value_type)
  z = convert_type(0, value_type)
  data.map do |ft|
    vec = Array.new(n_features) { z }
    ft.each { |idx, val| vec[idx] = val }
    vec
  end
end

convert_type(value, dtype) click to toggle source

# File lib/libsvmloader.rb, line 78
def convert_type(value, dtype)
  case dtype
  when :int
    value.to_i
  when :float
    value.to_f
  when :complex
    value.to_c
  else
    value
  end
end

detect_format(data) click to toggle source

# File lib/libsvmloader.rb, line 100
def detect_format(data)
  type = '%s'
  type = '%d' if data.is_a?(Integer)
  type = '%.10g' if data.is_a?(Float)
  type
end

dump_libsvm_line(label, ftvec, label_format, value_format, zero_based) click to toggle source

# File lib/libsvmloader.rb, line 107
def dump_libsvm_line(label, ftvec, label_format, value_format, zero_based)
  line = format(label_format, label)
  ftvec.each_with_index do |val, n|
    unless val.zero?
      idx = n + (zero_based == false ? 1 : 0)
      line += format(" %d:#{value_format}", idx, val)
    end
  end
  line
end

parse_dtype(dtype) click to toggle source

# File lib/libsvmloader.rb, line 65
def parse_dtype(dtype)
  case dtype.to_s
  when /^(int)/i
    :int
  when /^(float)/i
    :float
  when /^(complex)/i
    :complex
  else
    :string
  end
end

parse_libsvm_row(row, zero_based, label_type, value_type) click to toggle source

# File lib/libsvmloader.rb, line 51
def parse_libsvm_row(row, zero_based, label_type, value_type)
  label = convert_type(row.shift, label_type)
  adj_idx = zero_based == false ? 1 : 0
  max_idx = -1
  ftvec = []
  while (el = row.shift)
    idx, val = el.split(':')
    idx = idx.to_i - adj_idx
    max_idx = idx if max_idx < idx
    ftvec.push([idx, convert_type(val, value_type)])
  end
  [label, ftvec, max_idx]
end