Dynamically create plots in Chaco

Question

The Chaco plotting toolkit for Python includes examples that show how to dynamically update existing plots. However, my application requires that I dynamically create and destroy plots depending on the data. I am new to programming with Chaco and Traits, so a simple example that illustrates how to do this would be really helpful.

Answer 1

This is a bit late, but here's an example that creates and destroys Chaco plots. The main interface is PlotSelector , which defines some fake data and radio buttons to switch between two different plot styles (line and bar plots).

This example uses a Traits event to signal when to close a plot, and then handles that signal with PlotController . There may be a better way to close the window, but I couldn't find one.

Edit : Updated imports for newer versions of Traits, Chaco, and Enable (ETS 4 instead of 3).

import numpy as np

import traits.api as traits
import traitsui.api as ui
import chaco.api as chaco
from enable.api import ComponentEditor


class PlotController(ui.Controller):
    view = ui.View(ui.Item('plot', editor=ComponentEditor(), show_label=False),
                   height=300, width=300, resizable=True)

    def object_close_signal_changed(self, info):
        info.ui.dispose()


class BasicPlot(traits.HasTraits):
    close_signal = traits.Event()
    plot = traits.Instance(chaco.Plot)


class LinePlot(BasicPlot):

    def __init__(self, plotdata):
        self.plot = chaco.Plot(plotdata)
        self.plot.plot(('x', 'y'))


class BarPlot(BasicPlot):

    def __init__(self, plotdata):
        self.plot = chaco.Plot(plotdata)
        self.plot.candle_plot(('x', 'ymin', 'ymax'))


available_plot_types = dict(line=LinePlot, bar=BarPlot)

class PlotSelector(traits.HasTraits):

    plot_type = traits.Enum(['line', 'bar'])
    traits_view = ui.View('plot_type', style='custom')

    def __init__(self, x, y):
        ymin = y - 1
        ymax = y + 1
        self.plotdata = chaco.ArrayPlotData(x=x, y=y, ymin=ymin, ymax=ymax)
        self.figure = None

    def _plot_type_changed(self):
        plot_class = available_plot_types[self.plot_type]
        if self.figure is not None:
            self.figure.close_signal = True
        self.figure = plot_class(self.plotdata)
        controller = PlotController(model=self.figure)
        controller.edit_traits()


N = 20
x = np.arange(N)
y = x + np.random.normal(size=N)
plot_selector = PlotSelector(x, y)
plot_selector.configure_traits()

Note that the main interface ( PlotSelector ) calls configure_traits (starts application), while the plots are viewed with edit_traits (called from within application). Also, note that this example calls edit_traits from PlotController instead of calling it from the model. You could instead move the view from PlotController to BasicPlot and set the handler method of that view to PlotController .

Finally, if you don't need to totally destroy the plot window, then you may want to look at the Plot object's delplot method, which destroys the * sub *plot (here the line plot or bar plot).

I hope that helps.