# Fourier Demo WXΒΆ

import numpy as np

import wx
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
from matplotlib.figure import Figure

class Knob(object):
"""
Knob - simple class with a "setKnob" method.
A Knob instance is attached to a Param instance, e.g., param.attach(knob)
Base class is for documentation purposes.
"""

def setKnob(self, value):
pass

class Param(object):
"""
The idea of the "Param" class is that some parameter in the GUI may have
several knobs that both control it and reflect the parameter's state, e.g.
a slider, text, and dragging can all change the value of the frequency in
the waveform of this example.
The class allows a cleaner way to update/"feedback" to the other knobs when
one is being changed.  Also, this class handles min/max constraints for all
the knobs.
Idea - knob list - in "set" method, knob object is passed as well
- the other knobs in the knob list have a "set" method which gets
called for the others.
"""

def __init__(self, initialValue=None, minimum=0., maximum=1.):
self.minimum = minimum
self.maximum = maximum
if initialValue != self.constrain(initialValue):
raise ValueError('illegal initial value')
self.value = initialValue
self.knobs = []

def attach(self, knob):
self.knobs += [knob]

def set(self, value, knob=None):
self.value = value
self.value = self.constrain(value)
for feedbackKnob in self.knobs:
if feedbackKnob != knob:
feedbackKnob.setKnob(self.value)
return self.value

def constrain(self, value):
if value <= self.minimum:
value = self.minimum
if value >= self.maximum:
value = self.maximum
return value

class SliderGroup(Knob):
def __init__(self, parent, label, param):
self.sliderLabel = wx.StaticText(parent, label=label)
self.sliderText = wx.TextCtrl(parent, -1, style=wx.TE_PROCESS_ENTER)
self.slider = wx.Slider(parent, -1)
# self.slider.SetMax(param.maximum*1000)
self.slider.SetRange(0, param.maximum * 1000)
self.setKnob(param.value)

sizer = wx.BoxSizer(wx.HORIZONTAL)
wx.EXPAND | wx.ALIGN_CENTER | wx.ALL,
border=2)
wx.EXPAND | wx.ALIGN_CENTER | wx.ALL,
border=2)
self.sizer = sizer

self.slider.Bind(wx.EVT_SLIDER, self.sliderHandler)
self.sliderText.Bind(wx.EVT_TEXT_ENTER, self.sliderTextHandler)

self.param = param
self.param.attach(self)

def sliderHandler(self, evt):
value = evt.GetInt() / 1000.
self.param.set(value)

def sliderTextHandler(self, evt):
value = float(self.sliderText.GetValue())
self.param.set(value)

def setKnob(self, value):
self.sliderText.SetValue('%g' % value)
self.slider.SetValue(value * 1000)

class FourierDemoFrame(wx.Frame):
def __init__(self, *args, **kwargs):
wx.Frame.__init__(self, *args, **kwargs)
panel = wx.Panel(self)

# create the GUI elements
self.createCanvas(panel)
self.createSliders(panel)

# place them in a sizer for the Layout
sizer = wx.BoxSizer(wx.VERTICAL)
wx.EXPAND | wx.ALIGN_CENTER | wx.ALL, border=5)
wx.EXPAND | wx.ALIGN_CENTER | wx.ALL, border=5)
panel.SetSizer(sizer)

def createCanvas(self, parent):
self.lines = []
self.figure = Figure()
self.canvas = FigureCanvas(parent, -1, self.figure)
self.canvas.callbacks.connect('button_press_event', self.mouseDown)
self.canvas.callbacks.connect('motion_notify_event', self.mouseMotion)
self.canvas.callbacks.connect('button_release_event', self.mouseUp)
self.state = ''
self.mouseInfo = (None, None, None, None)
self.f0 = Param(2., minimum=0., maximum=6.)
self.A = Param(1., minimum=0.01, maximum=2.)
self.createPlots()

# Not sure I like having two params attached to the same Knob,
# but that is what we have here... it works but feels kludgy -
# although maybe it's not too bad since the knob changes both params
# at the same time (both f0 and A are affected during a drag)
self.f0.attach(self)
self.A.attach(self)

def createSliders(self, panel):
self.frequencySliderGroup = SliderGroup(
panel,
label='Frequency f0:',
param=self.f0)
self.amplitudeSliderGroup = SliderGroup(panel, label=' Amplitude a:',
param=self.A)

def mouseDown(self, evt):
if self.lines[0].contains(evt)[0]:
self.state = 'frequency'
elif self.lines[1].contains(evt)[0]:
self.state = 'time'
else:
self.state = ''
self.mouseInfo = (evt.xdata, evt.ydata,
max(self.f0.value, .1),
self.A.value)

def mouseMotion(self, evt):
if self.state == '':
return
x, y = evt.xdata, evt.ydata
if x is None:  # outside the axes
return
x0, y0, f0Init, AInit = self.mouseInfo
self.A.set(AInit + (AInit * (y - y0) / y0), self)
if self.state == 'frequency':
self.f0.set(f0Init + (f0Init * (x - x0) / x0))
elif self.state == 'time':
if (x - x0) / x0 != -1.:
self.f0.set(1. / (1. / f0Init + (1. / f0Init * (x - x0) / x0)))

def mouseUp(self, evt):
self.state = ''

def createPlots(self):
# This method creates the subplots, waveforms and labels.
# Later, when the waveforms or sliders are dragged, only the
# waveform data will be updated (not here, but below in setKnob).
if not hasattr(self, 'subplot1'):
self.subplot1, self.subplot2 = self.figure.subplots(2)
x1, y1, x2, y2 = self.compute(self.f0.value, self.A.value)
color = (1., 0., 0.)
self.lines += self.subplot1.plot(x1, y1, color=color, linewidth=2)
self.lines += self.subplot2.plot(x2, y2, color=color, linewidth=2)
# Set some plot attributes
self.subplot1.set_title(
"Click and drag waveforms to change frequency and amplitude",
fontsize=12)
self.subplot1.set_ylabel("Frequency Domain Waveform X(f)", fontsize=8)
self.subplot1.set_xlabel("frequency f", fontsize=8)
self.subplot2.set_ylabel("Time Domain Waveform x(t)", fontsize=8)
self.subplot2.set_xlabel("time t", fontsize=8)
self.subplot1.set_xlim([-6, 6])
self.subplot1.set_ylim([0, 1])
self.subplot2.set_xlim([-2, 2])
self.subplot2.set_ylim([-2, 2])
self.subplot1.text(0.05, .95,
r'$X(f) = \mathcal{F}\{x(t)\}$',
verticalalignment='top',
transform=self.subplot1.transAxes)
self.subplot2.text(0.05, .95,
r'$x(t) = a \cdot \cos(2\pi f_0 t) e^{-\pi t^2}$',
verticalalignment='top',
transform=self.subplot2.transAxes)

def compute(self, f0, A):
f = np.arange(-6., 6., 0.02)
t = np.arange(-2., 2., 0.01)
x = A * np.cos(2 * np.pi * f0 * t) * np.exp(-np.pi * t ** 2)
X = A / 2 * \
(np.exp(-np.pi * (f - f0) ** 2) + np.exp(-np.pi * (f + f0) ** 2))
return f, X, t, x

def setKnob(self, value):
# Note, we ignore value arg here and just go by state of the params
x1, y1, x2, y2 = self.compute(self.f0.value, self.A.value)
# update the data of the two waveforms
self.lines[0].set(xdata=x1, ydata=y1)
self.lines[1].set(xdata=x2, ydata=y2)
# make the canvas draw its contents again with the new data
self.canvas.draw()

class App(wx.App):
def OnInit(self):
self.frame1 = FourierDemoFrame(parent=None, title="Fourier Demo",
size=(640, 480))
self.frame1.Show()
return True

app = App()
app.MainLoop()


Keywords: matplotlib code example, codex, python plot, pyplot Gallery generated by Sphinx-Gallery