[sage-support] Re: Vector fields and Quivers
Thanks for the matplotlib recipe! I just had the same problem with plot_vector_field not accepting coordinate functions of two arguments. I went ahead and created an issue: http://trac.sagemath.org/sage_trac/ticket/2381 - Eric On Feb 17, 10:19 am, Hector Villafuerte [EMAIL PROTECTED] wrote: Hi, I would like to plot the gradient (i.e. vector field) of functions such as f(x,y) = exp(-(x^2 + y^2)); in this case: grad(f(x,y)) = vector([ -2*x*exp(-(x^2 + y^2)), -2*y*exp(-(x^2 + y^2)) ]) Initially I tried with plot_vector_field, but as of now it just takes two functions of one variable. For my second attempt I used matplotlib, as indicated below (also, see attached plots). So my question: is there a SAGEly way to plot this type of vector fields? Thanks in advance! -- Hector sage: %python sage: from pylab import * sage: X,Y = meshgrid( arange(-2,2,.2),arange(-2,2,.2) ) sage: U = -2*X*exp(-(X*X + Y*Y)) sage: V = -2*Y*exp(-(X*X + Y*Y)) sage: figure() sage: Q = quiver( U, V) sage: l,r,b,t = axis() sage: dx, dy = r-l, t-b sage: axis([l-0.05*dx, r+0.05*dx, b-0.05*dy, t+0.05*dy]) sage: savefig(DATA+'quiver.png') quiver.png 96KViewDownload 3d.png 1020KViewDownload --~--~-~--~~~---~--~~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~--~~~~--~~--~--~---
[sage-support] Re: Vector fields and Quivers
Jason: wow, that was quick. I'll try out the plot_vector_field patch
as soon as I figure out how to test patches etc
I ended up using Hector's example and some things from the matplotlib
documentation for my assignment. A notable improvement is using
axis('tight'), which solves the window mis-alignment problem.
Uploaded to https://www.sagenb.org/home/pub/1721
On Mar 3, 8:34 pm, Eric Drechsel [EMAIL PROTECTED] wrote:
Thanks for the matplotlib recipe! I just had the same problem with
plot_vector_field not accepting coordinate functions of two arguments.
I went ahead and created an
issue:http://trac.sagemath.org/sage_trac/ticket/2381
- Eric
On Feb 17, 10:19 am, Hector Villafuerte [EMAIL PROTECTED] wrote:
Hi,
I would like to plot the gradient (i.e. vector field) of functions
such as f(x,y) = exp(-(x^2 + y^2)); in this case:
grad(f(x,y)) = vector([ -2*x*exp(-(x^2 + y^2)), -2*y*exp(-(x^2 + y^2)) ])
Initially I tried with plot_vector_field, but as of now it just takes
two functions of one variable. For my second attempt I used
matplotlib, as indicated below (also, see attached plots).
So my question: is there a SAGEly way to plot this type of vector fields?
Thanks in advance!
--
Hector
sage: %python
sage: from pylab import *
sage: X,Y = meshgrid( arange(-2,2,.2),arange(-2,2,.2) )
sage: U = -2*X*exp(-(X*X + Y*Y))
sage: V = -2*Y*exp(-(X*X + Y*Y))
sage: figure()
sage: Q = quiver( U, V)
sage: l,r,b,t = axis()
sage: dx, dy = r-l, t-b
sage: axis([l-0.05*dx, r+0.05*dx, b-0.05*dy, t+0.05*dy])
sage: savefig(DATA+'quiver.png')
quiver.png
96KViewDownload
3d.png
1020KViewDownload
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[sage-support] Re: Vector fields and Quivers
Hector Villafuerte wrote:
Hi,
I would like to plot the gradient (i.e. vector field) of functions
such as f(x,y) = exp(-(x^2 + y^2)); in this case:
grad(f(x,y)) = vector([ -2*x*exp(-(x^2 + y^2)), -2*y*exp(-(x^2 + y^2)) ])
Initially I tried with plot_vector_field, but as of now it just takes
two functions of one variable. For my second attempt I used
matplotlib, as indicated below (also, see attached plots).
So my question: is there a SAGEly way to plot this type of vector fields?
Thanks in advance!
There is now! It turned out to be a pretty simple fix to
plot_vector_field; see http://trac.sagemath.org/sage_trac/ticket/2381
Here's an example:
sage: x,y=var('x y')
sage: f(x,y) = exp(-(x^2+y^2))
sage: grad_f = [diff(f,var) for var in (x,y)]
sage: plot_vector_field(grad_f, (-2,2), (-2,2))
Thanks,
Jason
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