Displays a matrix with scatter plot for each pair of 
	Series in the DataFrame.
	The diagonal shows a histogram for each of the Series

	Parameters:
	-----------
		df : DataFrame
			Pandas DataFrame
		theme : string
			Theme to be used (if not the default)
		bins : int
			Number of bins to use for histogram
		color : string
			Color to be used for each scatter plot
		size : int
			Size for each marker on the scatter plot
		iplot_kwargs : key-value pairs
			Keyword arguments to pass through to `iplot`

def _scatter_matrix(self,theme=None,bins=10,color='grey',size=2, asFigure=False, **iplot_kwargs):
	"""
	Displays a matrix with scatter plot for each pair of 
	Series in the DataFrame.
	The diagonal shows a histogram for each of the Series

	Parameters:
	-----------
		df : DataFrame
			Pandas DataFrame
		theme : string
			Theme to be used (if not the default)
		bins : int
			Number of bins to use for histogram
		color : string
			Color to be used for each scatter plot
		size : int
			Size for each marker on the scatter plot
		iplot_kwargs : key-value pairs
			Keyword arguments to pass through to `iplot`
	"""
	sm=tools.scatter_matrix(self,theme=theme,bins=bins,color=color,size=size)
	if asFigure:
		return sm
	else:
		return iplot(sm,**iplot_kwargs)