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Re: [Matplotlib-users] streamplot: vectors not pointing in the right direction!
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From: Gabriele B. <gb....@gm...> - 2015-05-22 15:14:22
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Thanks! you are right! I didn't notice this detail Gabriele On Fri, May 22, 2015 at 3:58 PM, Benjamin Root <ben...@ou...> wrote: > The documentation for streamplot: > > ``` > *x*, *y* : 1d arrays > an *evenly spaced* grid. > *u*, *v* : 2d arrays > x and y-velocities. Number of rows should match length of y, > and > the number of columns should match x. > ``` > > Note that the rows in *u* and *v* should match *y*, and the columns should > match *x*. I think your *u* and *v* are transposed. > > Cheers! > Ben Root > > > On Fri, May 22, 2015 at 2:50 AM, Gabriele Brambilla < > gb....@gm...> wrote: > >> Hi, >> >> I have problems with streamplot >> >> I want to use a 3d vector field in coordinates (x,y,z) stored in a numpy >> array, and plot slices of it with streamplot. >> >> To test it I wanted to use a vector field with arrows pointed up in the >> z>0 region and pointed down in the z<0 region. >> >> >> import numpy as np >> >> import matplotlib.pyplot as plt >> >> from math import * >> >> >> >> max = 100 >> >> min = -100 >> >> >> >> >> >> X = np.linspace(min, max, num=100) >> >> Y = np.linspace(min, max, num=100) >> >> Z = np.linspace(min, max, num=100) >> >> >> >> N = X.size >> >> >> >> #single components in the 3D matrix >> >> >> Bxa = np.zeros((N, N, N)) >> >> Bya = np.zeros((N, N, N)) >> >> Bza = np.zeros((N, N, N)) >> >> >> >> >> >> for i, x in enumerate(X): >> >> for j, y in enumerate(Y): >> >> for k, z in enumerate(Z): >> >> Bxa[ i, j, k] = 0.0 #x >> >> Bya[ i, j, k] = 0.0 #y >> >> Bza[ i, j, k] = z >> >> >> >> #I take a slice close to Y=0 >> >> Bx_sec = Bxa[:,N/2,:] >> >> By_sec = Bya[:,N/2,:] >> >> Bz_sec = Bza[:,N/2,:] >> >> >> >> fig = plt.figure() >> >> ax = fig.add_subplot(111) >> >> ax.streamplot(X, Z, Bx_sec, Bz_sec, color='b') >> >> ax.set_xlim([X.min(), X.max()]) >> >> ax.set_ylim([Z.min(), Z.max()]) >> >> >> >> plt.show() >> >> >> But I obtain something that looks like if I have put Bza = x! I tried to >> invert the order of vectors but it is unuseful! >> >> I attach the picture. Do you understand why? (the code I posted should >> run) >> >> Gabriele >> >> >> ------------------------------------------------------------------------------ >> One dashboard for servers and applications across Physical-Virtual-Cloud >> Widest out-of-the-box monitoring support with 50+ applications >> Performance metrics, stats and reports that give you Actionable Insights >> Deep dive visibility with transaction tracing using APM Insight. >> http://ad.doubleclick.net/ddm/clk/290420510;117567292;y >> _______________________________________________ >> Matplotlib-users mailing list >> Mat...@li... >> https://lists.sourceforge.net/lists/listinfo/matplotlib-users >> >> > |
