Plot DataFrame columns as lines.

        This function is useful to plot lines using DataFrame's values
        as coordinates.

        Parameters
        ----------
        x : int or str, optional
            Columns to use for the horizontal axis.
            Either the location or the label of the columns to be used.
            By default, it will use the DataFrame indices.
        y : int, str, or list of them, optional
            The values to be plotted.
            Either the location or the label of the columns to be used.
            By default, it will use the remaining DataFrame numeric columns.
        **kwds
            Keyword arguments to pass on to :meth:`DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or :class:`numpy.ndarray`
            Return an ndarray when ``subplots=True``.

        See Also
        --------
        matplotlib.pyplot.plot : Plot y versus x as lines and/or markers.

        Examples
        --------

        .. plot::
            :context: close-figs

            The following example shows the populations for some animals
            over the years.

            >>> df = pd.DataFrame({
            ...    'pig': [20, 18, 489, 675, 1776],
            ...    'horse': [4, 25, 281, 600, 1900]
            ...    }, index=[1990, 1997, 2003, 2009, 2014])
            >>> lines = df.plot.line()

        .. plot::
           :context: close-figs

           An example with subplots, so an array of axes is returned.

           >>> axes = df.plot.line(subplots=True)
           >>> type(axes)
           <class 'numpy.ndarray'>

        .. plot::
            :context: close-figs

            The following example shows the relationship between both
            populations.

            >>> lines = df.plot.line(x='pig', y='horse')

def line(self, x=None, y=None, **kwds):
        """
        Plot DataFrame columns as lines.

        This function is useful to plot lines using DataFrame's values
        as coordinates.

        Parameters
        ----------
        x : int or str, optional
            Columns to use for the horizontal axis.
            Either the location or the label of the columns to be used.
            By default, it will use the DataFrame indices.
        y : int, str, or list of them, optional
            The values to be plotted.
            Either the location or the label of the columns to be used.
            By default, it will use the remaining DataFrame numeric columns.
        **kwds
            Keyword arguments to pass on to :meth:`DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or :class:`numpy.ndarray`
            Return an ndarray when ``subplots=True``.

        See Also
        --------
        matplotlib.pyplot.plot : Plot y versus x as lines and/or markers.

        Examples
        --------

        .. plot::
            :context: close-figs

            The following example shows the populations for some animals
            over the years.

            >>> df = pd.DataFrame({
            ...    'pig': [20, 18, 489, 675, 1776],
            ...    'horse': [4, 25, 281, 600, 1900]
            ...    }, index=[1990, 1997, 2003, 2009, 2014])
            >>> lines = df.plot.line()

        .. plot::
           :context: close-figs

           An example with subplots, so an array of axes is returned.

           >>> axes = df.plot.line(subplots=True)
           >>> type(axes)
           <class 'numpy.ndarray'>

        .. plot::
            :context: close-figs

            The following example shows the relationship between both
            populations.

            >>> lines = df.plot.line(x='pig', y='horse')
        """
        return self(kind='line', x=x, y=y, **kwds)