"""Polynomial explorer. You tell this module what order of polynomial you want and it will set up a figure
with a graph of that polynomial plotted with x = -1 to +1. It will set up a second figure with a set of
coefficient axes. You can click on the coeffiecient axes to set the coefficents. The graph will then update
to reflect the values of the new coefficients"""
import pylab as M
def f(x,c):
"""Pass in x (a scalar or vector) and pass in c (a vector) and this function will compute
f(x) = x**n + c(n-1)*x**(n-1) ... + c(1)*x + c(0)"""
N = len(c)
y = M.zeros(len(x))
for n in xrange(N):
y += c[n]*x**n
y += x**N
return y
def fstring(c):
"""Pass the coefficients and return a string corresponding to the ploynomial"""
order = len(c)
fx = "$f(x) = x^%d" %(order)
for n in xrange(order-1):
nn = order - 1 - n
fx += " + %1.3f x^%d" %(c[nn],nn)
fx += " + %1.3f$" %(c[0])
return fx
class Explorer:
def __init__(self, norder = 2):
"""Initializes the class when returning an instance. Pass it the polynomial order. It will
set up two figure windows, one for the graph the other for the coefficent interface. It will then initialize
the coefficients to zero and plot the (not so interesting) polynomial."""
self.order = norder
self.c = M.zeros(self.order,'f')
self.ax = [None]*(self.order-1)#M.zeros(self.order-1,'i') #Coefficent axes
self.ffig = M.figure() #The first figure window has the plot
self.replotf()
self.cfig = M.figure() #The second figure window has the
row = M.ceil(M.sqrt(self.order-1))
for n in xrange(self.order-1):
self.ax[n] = M.subplot(row, row, n+1)
M.setp(self.ax[n],'label', n)
M.plot([0],[0],'.')
M.axis([-1, 1, -1, 1]);
self.replotc()
M.connect('button_press_event', self.click_event)
def replotf(self):
"""This replots the function given the coefficient array c."""
x = M.arange(-1,1.,.001)
M.ioff()
M.figure(self.ffig.number)
M.cla()
M.plot(x, f(x,self.c))
M.title(fstring(self.c))
M.draw()
def replotc(self):
"""This replots the coefficients."""
M.figure(self.cfig.number)
M.ioff()
for n in xrange(self.order-1):
M.axes(self.ax[n])
#M.cla()
M.plot([self.c[n]], [self.c[n+1]],'ko')
M.xlabel("$c_%d$" %(n))
M.ylabel("$c_%d$" %(n+1))
M.axis([-1, 1, -1, 1]);
del self.ax[n].lines[0]
M.draw()
def click_event(self, event):
"""Whenever a click occurs on the coefficent axes we modify the coefficents and update the
plot"""
if event.xdata is None:#we clicked outside the axis
return
idx = M.getp(event.inaxes,'label')
print idx, event.xdata, event.ydata
self.c[idx] = event.xdata
self.c[idx+1] = event.ydata
self.replotf()
self.replotc()
