def view_umatrix(self, figsize=None, colormap=cm.Spectral_r,
                     colorbar=False, bestmatches=False, bestmatchcolors=None,
                     labels=None, zoom=None, filename=None):
        """Plot the U-matrix of the trained map.

        :param figsize: Optional parameter to specify the size of the figure.
        :type figsize: (int, int)
        :param colormap: Optional parameter to specify the color map to be
                         used.
        :type colormap: matplotlib.colors.Colormap
        :param colorbar: Optional parameter to include a colormap as legend.
        :type colorbar: bool.
        :param bestmatches: Optional parameter to plot best matching units.
        :type bestmatches: bool.
        :param bestmatchcolors: Optional parameter to specify the color of each
                                best matching unit.
        :type bestmatchcolors: list of int.
        :param labels: Optional parameter to specify the label of each point.
        :type labels: list of str.
        :param zoom: Optional parameter to zoom into a region on the map. The
                     first two coordinates of the tuple are the row limits, the
                     second tuple contains the column limits.
        :type zoom: ((int, int), (int, int))
        :param filename: If specified, the plot will not be shown but saved to
                         this file.
        :type filename: str.
        """
        if self.umatrix is None:
            raise Exception("The U-matrix is not available. Either train a map"
                            " or load a U-matrix from a file")
        return self._view_matrix(self.umatrix, figsize, colormap, colorbar,
                                 bestmatches, bestmatchcolors, labels, zoom,
                                 filename)
Plot the U-matrix of the trained map.

        :param figsize: Optional parameter to specify the size of the figure.
        :type figsize: (int, int)
        :param colormap: Optional parameter to specify the color map to be
                         used.
        :type colormap: matplotlib.colors.Colormap
        :param colorbar: Optional parameter to include a colormap as legend.
        :type colorbar: bool.
        :param bestmatches: Optional parameter to plot best matching units.
        :type bestmatches: bool.
        :param bestmatchcolors: Optional parameter to specify the color of each
                                best matching unit.
        :type bestmatchcolors: list of int.
        :param labels: Optional parameter to specify the label of each point.
        :type labels: list of str.
        :param zoom: Optional parameter to zoom into a region on the map. The
                     first two coordinates of the tuple are the row limits, the
                     second tuple contains the column limits.
        :type zoom: ((int, int), (int, int))
        :param filename: If specified, the plot will not be shown but saved to
                         this file.
        :type filename: str.