.. _pylab_examples-quiver_demo: pylab_examples example code: quiver_demo.py =========================================== .. plot:: /home/tcaswell/other_source/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. ''' from pylab import * from numpy import ma X,Y = meshgrid( arange(0,2*pi,.2),arange(0,2*pi,.2) ) U = cos(X) V = sin(Y) #1 figure() Q = quiver( U, V) qk = quiverkey(Q, 0.5, 0.92, 2, r'$2 \frac{m}{s}$', labelpos='W', fontproperties={'weight': 'bold'}) l,r,b,t = axis() dx, dy = r-l, t-b axis([l-0.05*dx, r+0.05*dx, b-0.05*dy, t+0.05*dy]) title('Minimal arguments, no kwargs') #2 figure() Q = quiver( X, Y, U, V, units='width') qk = quiverkey(Q, 0.9, 0.95, 2, r'$2 \frac{m}{s}$', labelpos='E', coordinates='figure', fontproperties={'weight': 'bold'}) axis([-1, 7, -1, 7]) title('scales with plot width, not view') #3 figure() Q = quiver( X[::3, ::3], Y[::3, ::3], U[::3, ::3], V[::3, ::3], pivot='mid', color='r', units='inches' ) qk = quiverkey(Q, 0.5, 0.03, 1, r'$1 \frac{m}{s}$', fontproperties={'weight': 'bold'}) plot( X[::3, ::3], Y[::3, ::3], 'k.') axis([-1, 7, -1, 7]) title("pivot='mid'; every third arrow; units='inches'") #4 figure() M = sqrt(pow(U, 2) + pow(V, 2)) Q = quiver( X, Y, U, V, M, units='x', pivot='tip', width=0.022, scale=1/0.15) qk = quiverkey(Q, 0.9, 1.05, 1, r'$1 \frac{m}{s}$', labelpos='E', fontproperties={'weight': 'bold'}) plot(X, Y, 'k.') axis([-1, 7, -1, 7]) title("scales with x view; pivot='tip'") #5 figure() Q = quiver( X[::3, ::3], Y[::3, ::3], U[::3, ::3], V[::3, ::3], color='r', units='x', linewidths=(2,), edgecolors=('k'), headaxislength=5 ) qk = quiverkey(Q, 0.5, 0.03, 1, r'$1 \frac{m}{s}$', fontproperties={'weight': 'bold'}) axis([-1, 7, -1, 7]) title("triangular head; scale with x view; black edges") #6 figure() M = 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 = quiver( U, V) qk = quiverkey(Q, 0.5, 0.92, 2, r'$2 \frac{m}{s}$', labelpos='W', fontproperties={'weight': 'bold'}) l,r,b,t = axis() dx, dy = r-l, t-b axis([l-0.05*dx, r+0.05*dx, b-0.05*dy, t+0.05*dy]) title('Minimal arguments, no kwargs - masked values') show() Keywords: python, matplotlib, pylab, example, codex (see :ref:how-to-search-examples)