Hi David,
El sáb, 06-02-2010 a las 10:21 -0800, David Arnold escribió:
> Hi Eric,
>
> Matlab has two commands, comet and comet3, that animate the path. They are
> used as in the following Matlab code:
>
> t=linspace(0,2*pi,2000);
> x=-sin(t);
> y=cos(t);
> comet(x,y)
You can just write the function:
import matplotlib.pyplot as plt
def comet(x, y, fmt='', step=1, **kwargs):
l, = plt.plot(x, y, fmt, **kwargs)
num_points = len(x)
for i in xrange(1, num_points + 1, step):
l.set_data(x[:i], y[:i])
plt.draw()
l.set_data(x, y)
plt.draw()
I think this could be better done using animation features of
matplotlib, but I never used them and I think they varies across
toolkits. Search the docs for animation examples anyway.
Goyo
>
> What then happens is the path is drawn "live", as in my python code below.
>
> This is especially useful when teaching parametric equations in calculus. A
> typical question in that section might be: "find a parametrization for the
> unit circle that starts at (0,1) and moves around the circle one time in the
> counterclockwise direction." In this situation, the following is not helpful:
>
> t=linspace(0,2*pi,2000);
> x=-sin(t);
> y=cos(t);
> plot(x,y)
>
> Because the student just sees sees the "finished" path. The comet command, on
> the other hand, allows the student to "see" that path as it is traced out in
> real time.
>
> David.
>
> On Feb 6, 2010, at 9:09 AM, Eric Firing wrote:
>
> > David Arnold wrote:
> >> All,
> >> I am still wondering why there is no comet command in matplotlib. I was
> >> successful with the following:
> >> import matplotlib.pyplot as plt
> >> import numpy as np
> >> len=200
> >> t=np.linspace(0,2*np.pi,len)
> >> x=np.cos(t)
> >> y=np.sin(t)
> >> xd=[x[0]]
> >> yd=[y[0]]
> >> l,=plt.plot(xd,yd)
> >> plt.axis([-1,1,-1,1])
> >> for i in np.arange(1,len):
> >> xd.append(x[i])
> >> yd.append(y[i])
> >> l.set_xdata(xd)
> >> l.set_ydata(yd)
> >> plt.draw()
> >>
> >> plt.show()
> >> But it seems that a comet function added to the matplotlib library would
> >> greatly simplify things for students using the interactive pylab in
> >> ipython.
> >
> > I don't understand--what's the point of the example? What is "comet", and
> > how does it simplify anything?
> >
> > Eric
> >
>
>
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