On Sun, Jul 1, 2012 at 12:50 PM, surfcast23 <surfcas...@gmail.com> wrote:
>
> Hi,
> I am translating a Matlab code to python and get the following error when
> the codes reaches the plotting section
>
> Warning (from warnings module):
> File "C:\Documents and Settings\My Documents\PHYSICS\Wave-eqn.py", line
> 40
> w = (D*v)
> RuntimeWarning: overflow encountered in multiply
> Traceback (most recent call last):
> File "C:\Documents and Settings\My Documents\PHYSICS\Wave-eqn\.py", line
> 50, in <module>
> ax.plot_wireframe(x,tdata,data, rstride=10, cstride=10)
> File "C:\Python32\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line
> 906, in plot_wireframe
> tylines = [tY[i] for i in cii]
> File "C:\Python32\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line
> 906, in <listcomp>
> tylines = [tY[i] for i in cii]
> IndexError: index out of bounds
>
> My code
>
> import numpy as np
> from numpy import *
> from math import pi
> from scipy.linalg import toeplitz
> from scipy.special import cotdg
> from mpl_toolkits.mplot3d import axes3d
> import matplotlib.pyplot as plt
>
>
>
> N = 512
> h = 2*np.pi/N
> x = h*(np.arange(N) + 1)
> t = 0
> dt = h / 4
> a = .1
> tmax = 15;
> tplot = .15;
> nplots = int(round((tmax/tplot)));
> plotgap = int(around(tplot/dt));
> c = a + np.sin(x - 1)**2
> v = np.exp(-100 * (x - 1)**2)
> vold = np.exp(-100 * (x - a*dt - 1)**2)
>
> #i = np.arange(1, N)
> #column = np.hstack([0, .5 * (-1**i) * cotdg(i * h/2)])
> #D = toeplitz(column, -column)
>
> column = ((0.5*(-1)**arange(1,N+1))*cotdg(arange(1,N+1))*(h/2));
> D = toeplitz(column,-column);print(D.shape);
>
> k = np.zeros(((nplots,N))); print(v.shape);print(k.shape);
> data = np.concatenate((v.reshape((512,1)).transpose(), k))#data =
> np.concatenate((v, k),axis = 1);
> #data = np.vstack([v,k]);
> tdata = t;
>
> for i in range(1,nplots+1):
> for n in range(1,plotgap+1):
> t = t+dt
> w = (D*v)
> vnew = vold-2*dt*c*w
> vold = v
> v = vnew
> data[i,:] = v[0,:]
> tdata = vstack([tdata, t])
>
> fig = plt.figure()
> ax = fig.add_subplot(111, projection='3d')
> #X, Y, Z = axes3d.get_test_data(0.05)
> ax.plot_wireframe(x,tdata,data, rstride=10, cstride=10)
>
> plt.show()
>
> I looked at the error line and it seems as if the y axes is where the
> problem is, but I am not seeing why and would appreciate any help. Thank
> you!
>
numpy arrays are indexed starting at 0, not 1. So when you populate your
"data" array with "data[i,:] = v[0,:]", and "i" only goes from 1 to nplots,
data[0,:] is left completely uninitialized (unless it is being done by some
of your pre-for-loop code, which is confusing to understand.)
What I can tell you is that the error isn't in plot_wireframe() as much as
the error exist with the inputs to plot_wireframe(). Perhaps the shapes
aren't right or something. I will try and look at your code closer
tomorrow and see if I can figure it out, but I suggest double-checking
those arrays.
Cheers!
Ben Root
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