.. _pylab_examples-quiver_demo: pylab_examples example code: quiver_demo.py =========================================== .. plot:: /home/tcaswell/source/p/matplotlib/doc/mpl_examples/pylab_examples/quiver_demo.py :: ''' Demonstration of quiver and quiverkey functions. This is using the new version coming from the code in quiver.py. Known problem: the plot autoscaling does not take into account the arrows, so those on the boundaries are often out of the picture. This is *not* an easy problem to solve in a perfectly general way. The workaround is to manually expand the axes. ''' import matplotlib.pyplot as plt import numpy as np from numpy import ma X, Y = np.meshgrid(np.arange(0, 2 * np.pi, .2), np.arange(0, 2 * np.pi, .2)) U = np.cos(X) V = np.sin(Y) # 1 plt.figure() Q = plt.quiver(U, V) qk = plt.quiverkey(Q, 0.5, 0.92, 2, r'$2 \frac{m}{s}$', labelpos='W', fontproperties={'weight': 'bold'}) l, r, b, t = plt.axis() dx, dy = r - l, t - b plt.axis([l - 0.05*dx, r + 0.05*dx, b - 0.05*dy, t + 0.05*dy]) plt.title('Minimal arguments, no kwargs') # 2 plt.figure() Q = plt.quiver(X, Y, U, V, units='width') qk = plt.quiverkey(Q, 0.9, 0.95, 2, r'$2 \frac{m}{s}$', labelpos='E', coordinates='figure', fontproperties={'weight': 'bold'}) plt.axis([-1, 7, -1, 7]) plt.title('scales with plot width, not view') # 3 plt.figure() Q = plt.quiver(X[::3, ::3], Y[::3, ::3], U[::3, ::3], V[::3, ::3], pivot='mid', color='r', units='inches') qk = plt.quiverkey(Q, 0.5, 0.03, 1, r'$1 \frac{m}{s}$', fontproperties={'weight': 'bold'}) plt.plot(X[::3, ::3], Y[::3, ::3], 'k.') plt.axis([-1, 7, -1, 7]) plt.title("pivot='mid'; every third arrow; units='inches'") # 4 plt.figure() M = np.hypot(U, V) Q = plt.quiver(X, Y, U, V, M, units='x', pivot='tip', width=0.022, scale=1 / 0.15) qk = plt.quiverkey(Q, 0.9, 1.05, 1, r'$1 \frac{m}{s}$', labelpos='E', fontproperties={'weight': 'bold'}) plt.plot(X, Y, 'k.') plt.axis([-1, 7, -1, 7]) plt.title("scales with x view; pivot='tip'") # 5 plt.figure() Q = plt.quiver(X[::3, ::3], Y[::3, ::3], U[::3, ::3], V[::3, ::3], color='r', units='x', linewidths=(2,), edgecolors=('k'), headaxislength=5) qk = plt.quiverkey(Q, 0.5, 0.03, 1, r'$1 \frac{m}{s}$', fontproperties={'weight': 'bold'}) plt.axis([-1, 7, -1, 7]) plt.title("triangular head; scale with x view; black edges") # 6 plt.figure() M = np.zeros(U.shape, dtype='bool') M[U.shape[0]//3:2*U.shape[0]//3, U.shape[1]//3:2*U.shape[1]//3] = True U = ma.masked_array(U, mask=M) V = ma.masked_array(V, mask=M) Q = plt.quiver(U, V) qk = plt.quiverkey(Q, 0.5, 0.92, 2, r'$2 \frac{m}{s}$', labelpos='W', fontproperties={'weight': 'bold'}) l, r, b, t = plt.axis() dx, dy = r - l, t - b plt.axis([l - 0.05 * dx, r + 0.05 * dx, b - 0.05 * dy, t + 0.05 * dy]) plt.title('Minimal arguments, no kwargs - masked values') plt.show() Keywords: python, matplotlib, pylab, example, codex (see :ref:how-to-search-examples)