def gini(self):
        """
        geo.gini()

        Return computed Gini coefficient.
        """
        if self.count()>1:
            xsort = sorted(self.raster.data[self.raster.mask == False].flatten()) # increasing order
            y = np.cumsum(xsort)
            B = sum(y) / (y[-1] * len(xsort))
            return 1 + 1./len(xsort) - 2*B
        else:
            return 1