Module: Arrow::ColumnContainable

Included in:
RecordBatch, Table
Defined in:
lib/arrow/column-containable.rb

Instance Method Summary collapse

Instance Method Details

#[](name) ⇒ Column #[](index) ⇒ Column #[](range) ⇒ self.class #[](selectors) ⇒ self.class

Overloads:

  • #[](name) ⇒ Column

    Find a column that has the given name.

    Parameters:

    • name (String, Symbol) —

      The column name to be found.

    Returns:

    • (Column) —

      The found column.

    See Also:

  • #[](index) ⇒ Column

    Find the ‘index`-th column.

    Parameters:

    • index (Integer) —

      The index to be found.

    Returns:

    • (Column) —

      The found column.

    See Also:

  • #[](range) ⇒ self.class

    Selects columns that are in ‘range` and creates a new container only with the selected columns.

    Parameters:

    • range (Range) —

      The range to be selected.

    Returns:

    • (self.class) —

      The newly created container that only has selected columns.

    See Also:

  • #[](selectors) ⇒ self.class

    Selects columns that are selected by ‘selectors` and creates a new container only with the selected columns.

    Parameters:

    • selectors (Array) —

      The selectors that are used to select columns.

    Returns:

    • (self.class) —

      The newly created container that only has selected columns.

    See Also:



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# File 'lib/arrow/column-containable.rb', line 136

def [](selector)
  case selector
  when ::Array
    select_columns(*selector)
  when Range
    select_columns(selector)
  else
    find_column(selector)
  end
end

#column_names ⇒ ::Array<String>

Return column names in this object.

Returns:

  • (::Array<String>) —

    column names.

Since:

  • 11.0.0



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# File 'lib/arrow/column-containable.rb', line 152

def column_names
  @column_names ||= columns.collect(&:name)
end

#columns ⇒ Object 



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# File 'lib/arrow/column-containable.rb', line 20

def columns
  @columns ||= schema.n_fields.times.collect do |i|
    Column.new(self, i)
  end
end

#each_column(&block) ⇒ Object 



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# File 'lib/arrow/column-containable.rb', line 26

def each_column(&block)
  columns.each(&block)
end

#[](name) ⇒ Column #[](index) ⇒ Column

Overloads:

  • #[](name) ⇒ Column

    Find a column that has the given name.

    Parameters:

    • name (String, Symbol) —

      The column name to be found.

    Returns:

    • (Column) —

      The found column.

  • #[](index) ⇒ Column

    Find the ‘index`-th column.

    Parameters:

    • index (Integer) —

      The index to be found.

    Returns:

    • (Column) —

      The found column.



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# File 'lib/arrow/column-containable.rb', line 41

def find_column(name_or_index)
  case name_or_index
  when String, Symbol
    name = name_or_index.to_s
    index = schema.get_field_index(name)
    return nil if index == -1
    Column.new(self, index)
  when Integer
    index = name_or_index
    index += n_columns if index < 0
    return nil if index < 0 or index >= n_columns
    Column.new(self, index)
  else
    message = "column name or index must be String, Symbol or Integer: "
    message << name_or_index.inspect
    raise ArgumentError, message
  end
end

#select_columns(*selectors) {|column| ... } ⇒ self.class

Selects columns that are selected by ‘selectors` and/or `block` and creates a new container only with the selected columns.

Parameters:

  • selectors (Array<String, Symbol, Integer, Range>) —

    If a selector is ‘String`, `Symbol` or `Integer`, the selector selects a column by #find_column.

    If a selector is ‘Range`, the selector selects columns by `::Array#[]`.

Yields:

  • (column) —

    Gives a column to the block to select columns. This uses ‘::Array#select`.

Yield Parameters:

  • column (Column) —

    A target column.

Yield Returns:

  • (Boolean) —

    Whether the given column is selected or not.

Returns:

  • (self.class) —

    The newly created container that only has selected columns.



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# File 'lib/arrow/column-containable.rb', line 74

def select_columns(*selectors, &block)
  if selectors.empty?
    return to_enum(__method__) unless block_given?
    selected_columns = columns.select(&block)
  else
    selected_columns = []
    selectors.each do |selector|
      case selector
      when Range
        selected_columns.concat(columns[selector])
      else
        column = find_column(selector)
        if column.nil?
          case selector
          when String, Symbol
            message = "unknown column: #{selector.inspect}: #{inspect}"
            raise KeyError.new(message)
          else
            message = "out of index (0..#{n_columns - 1}): "
            message << "#{selector.inspect}: #{inspect}"
            raise IndexError.new(message)
          end
        end
        selected_columns << column
      end
    end
    selected_columns = selected_columns.select(&block) if block_given?
  end
  self.class.new(selected_columns)
end