trying a add multple line_plots to the Enthought zoom_plot.py example (https://github.com/enthought/chaco/tree/master/examples/demo/zoomed_plot) requires additional imports from that folder.

gistfile1.py

"""
The main executable file for the zoom_plot demo.

Right-click and drag on the upper plot to select a region to view in detail
in the lower plot. The selected region can be moved around by dragging,
or resized by clicking on one of its edges and dragging. The ZoomPlot class
encapsulates the creation of a zoom plot and exposes some of the attributes and
methods necessary for deep interaction with the plot.
"""
# Standard library imports
import os

# Major library imports
from numpy import sin, pi, linspace

# Enthought imports
from enable.api import Component, ComponentEditor
from traits.api import HasTraits, Instance
from traitsui.api import Item, Group, View
from traits.util.resource import find_resource

# Chaco imports
from chaco.api import VPlotContainer, ArrayPlotData, Plot, PlotGrid, PlotAxis
from chaco.tools.api import RangeSelection

# Relative imports
from zoom_overlay import ZoomOverlay

sample_path = os.path.join('examples','data','sample.wav')
alt_path = os.path.join('..','data','sample.wav')
fname = find_resource('Chaco', sample_path, alt_path=alt_path,
    return_path=True)
numpts = 3000

def read_music_data():
    from wav_to_numeric import wav_to_numeric
    index, data = wav_to_numeric(fname)
    return index[:numpts], data[:numpts]


class ZoomPlot(HasTraits):
    '''Encapsulation of the zoom plot concept.

This class organzies the data, plot container and ZoomOverlay required for
a zoom plot. ZoomPlot represents the first step towards a reusable and
extensible generalization of the zoom plot.

'''

    data = Instance(ArrayPlotData)

    plot = Instance(Component)
    
    def update_data(self, x, y):
        '''Update the data in the plot windows'''
        # FIXME: This isn't forcing the update, so the crufty code below is used.
        #self.plot.data['x'] = x
        #self.plot.data['y'] = y
        self.plot.components[0].index.set_data(x)
        self.plot.components[0].value.set_data(y)
        self.plot.components[1].index.set_data(x)
        self.plot.components[1].value.set_data(y)

    def _data_default(self):
        x = linspace(0, 4*pi, 1201)
        y = sin(x**2)
    	
        # NH - create an addtional data source to plot on the zoom_plot
        z = -1. * y
        
        data = ArrayPlotData(x=x, y=y, z=z)
        
        return data

    def _plot_default(self):
        plotter = Plot(data=self.data)
        main_plot = plotter.plot(['x','y'])[0]
        self.configure_plot(main_plot, xlabel='')

        # NH - add the additonal data to the Plot instance
        # this gets correctly added to plotter.plots but does not appear on 
		# the plot.  This appears to be the 'usual' way of doing things described at:
		# http://docs.enthought.com/chaco/user_manual/chaco_tutorial.html#multiple-plots 
        # Why is self.configure_plot called with main_plot, which 
		# is a plotter.plot instance, why not directly on plotter?  
        # self.configure_plot seems to add grids lines, set the bg color etc. of 
		# main_plot, which is a LinePlot instance.  I would have expected grid 
		# lines to added to the top most level??  
		
        plotter.plot(['x','z'])
		
		# NH - this does not work either
        # main_plot2 = plotter.plot(['x','z'])[0]
        # self.configure_plot(main_plot2, xlabel='')
        
        plotter2 = Plot(data=self.data)
        zoom_plot = plotter2.plot(['x','y'])[0]
        self.configure_plot(zoom_plot)
        
        outer_container = VPlotContainer(padding=20,
                                         fill_padding=True,
                                         spacing=0,
                                         stack_order='top_to_bottom',
                                         bgcolor='lightgray',
                                         use_backbuffer=True)

        outer_container.add(main_plot)
        outer_container.add(zoom_plot)
        # FIXME: This is set to the windows bg color. Should get from the system.
        #outer_container.bgcolor = (236/255., 233/255., 216/255., 1.0)

        main_plot.controller = RangeSelection(main_plot)
        
        zoom_overlay = ZoomOverlay(source=main_plot, destination=zoom_plot)
        outer_container.overlays.append(zoom_overlay)

        return outer_container

    @staticmethod
    def configure_plot(plot, xlabel='Time (s)'):
        """ Set up colors, grids, etc. on plot objects.
"""
        plot.bgcolor = 'white'
        plot.border_visible = True
        plot.padding = [40, 15, 15, 20]
        plot.color = 'darkred'
        plot.line_width = 1.1
        
        vertical_grid = PlotGrid(component=plot,
                                mapper=plot.index_mapper,
                                orientation='vertical',
                                line_color="gray",
                                line_style='dot',
                                use_draw_order = True)

        horizontal_grid = PlotGrid(component=plot,
                                mapper=plot.value_mapper,
                                orientation='horizontal',
                                line_color="gray",
                                line_style='dot',
                                use_draw_order = True)

        vertical_axis = PlotAxis(orientation='left',
                                mapper=plot.value_mapper,
                                use_draw_order = True)
        
        horizontal_axis = PlotAxis(orientation='bottom',
                                title=xlabel,
                                mapper=plot.index_mapper,
                                use_draw_order = True)

        plot.underlays.append(vertical_grid)
        plot.underlays.append(horizontal_grid)

        # Have to add axes to overlays because we are backbuffering the main plot,
        # and only overlays get to render in addition to the backbuffer.
        plot.overlays.append(vertical_axis)
        plot.overlays.append(horizontal_axis)
        
#===============================================================================
# Attributes to use for the plot view.
size = (800, 600)
title = fname

#===============================================================================
# # Demo class that is used by the demo.py application.
#===============================================================================
class ZoomPlotView(HasTraits):

    zoom_plot = Instance(ZoomPlot, ())
    
    traits_view = View(
                    Group(
                        Item('object.zoom_plot.plot', editor=ComponentEditor(size=size),
                             show_label=False),
                        orientation = "vertical"),
                    resizable=True, title='Zoom Plot',
                    width=size[0], height=size[1]
                    )

demo = ZoomPlotView()

# NH - comment out, use _data_default instead

# Configure the zoom plot by giving it data
#try:
    #x,y = read_music_data()
#    demo.zoom_plot.update_data(x, y)
#except:
    # Use the defaults
#    pass

if __name__ == "__main__":
    demo.configure_traits()

#--EOF---