2017-04-07 04:58:29 +0100 received badge ● Notable Question (source) 2015-03-20 10:09:31 +0100 received badge ● Nice Question (source) 2014-01-15 15:04:32 +0100 received badge ● Famous Question (source) 2013-12-23 16:17:08 +0100 received badge ● Popular Question (source) 2013-06-17 12:53:55 +0100 received badge ● Notable Question (source) 2013-03-03 03:07:50 +0100 received badge ● Popular Question (source) 2013-01-20 22:54:50 +0100 marked best answer Animation example from matplotlib.org does not work. I posted this answer in sage-support, but for completeness, I'll post it here as well. The following works for me: sage: from animate_decay import * sage: ani.save('blah.mp4')  2013-01-17 13:10:25 +0100 asked a question Animation example from matplotlib.org does not work. I'm trying to run thisexample from matplotlib.org. I downloaded the source code and ran: sage: load('animate_decay.py') sage: plt.savefig('foo.png') The file, foo.png, contained an empty Cartesian plane. I also typed in the code verbatim into the Sage interpreter and had the same results. I am running Sage Version 5.5, Release Date: 2012-12-22 on Ubuntu 12.04.1 LTS. Any suggestions would be greatly appreciated! 2012-11-11 06:46:17 +0100 received badge ● Student (source) 2012-10-17 13:57:51 +0100 commented answer Publishing worksheets in Wordpress, Blogger... Could you give a bit more detail in this answer, please? 2012-10-15 13:00:18 +0100 commented answer Phase portraits of 2-dimensional systems How can I restrict the max/min values in the solutions? Is there a uniform way to do this or restrict the axes' range (e.g., force the plot onto [-2,2]x[-2,2] ) 2012-10-15 00:48:02 +0100 received badge ● Supporter (source) 2012-10-15 00:48:00 +0100 marked best answer Phase portraits of 2-dimensional systems sage: maxima('plotdf([-y,-x],[x,y],[x,-2,2],[y,-2,2])')  Every click in the obtained field gives you a new trajectory Precise coordinates of an initial point can be provided in plot setup New x y coordinates + Enter adds a new trajectory 2012-10-15 00:47:59 +0100 received badge ● Scholar (source) 2012-10-15 00:20:50 +0100 commented answer Phase portraits of 2-dimensional systems @calc314: could you describe what happens when you enter the above code? 2012-10-14 15:02:40 +0100 asked a question Phase portraits of 2-dimensional systems I'm trying to plot solutions to two dimensional ordinary differential equations. I found that Sage makes it easy to plot a vector field and, using ode_solver(), I can plot solutions on top of the vector field by specifying an initial condition y_0 and some range of time to run (t_span). However, this method I'm using seems to be quite ad hoc, as I have to choose the right initial conditions and time span / know a lot about my system in order to plot a nice picture. Let's make this more concrete: Say I want to draw a nice phase portrait for $\dot{x} = -y$ $\dot{y} = -x$ First I generate the vector field: var('x y') VF=plot_vector_field([-y,-x],[x,-2,2],[y,-2,2])  Then I use ode_solver() to plot solutions with initial conditions going around the unit circle: T = ode_solver() T.function=lambda t,y:[-y[1],-y[0]] solutions = [] c = circle((0,0), 1, rgbcolor=(1,0,1)) for k in range(0,8): T.ode_solve(y_0=[cos(k*pi/4),sin(k*pi,t_span=[0,1],num_points=100) solutions.append(line([p[1] for p in T.solution]))  This generates the following picture: But if I change run the system for one more unit of time (set t_span=[0,2]), the picture gets skewed: This makes sense, of course, because the magnitude of the vectors along $y=-x$ get big as you get further away from the origin. Similarly, the trajectory along $y=x$ has trouble getting to the origin because the magnitude of those vectors get very small. Which all makes me think there's a better way to do this. Thoughts?