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2018-07-03 09:57:27 -0600 answered a question Getting convex hull of a set of points and plotting the polygon

Also

P1 = Polyhedron(vertices = [[-5,2], [4,4], [3,0], [1,0], [2,-4], [-3,-1], [-5,-3]])
P1.plot()

as in A Brief Introduction to Polytopes in Sage

2018-01-31 10:00:25 -0600 commented answer Can I generate 3D plots in isometric projection?

Very promising! I do see the menu when I right click on the plot, but the menu does not work, and the submenu does not display...

2018-01-29 08:18:14 -0600 commented question Is there CUDA support in Sage?

You can probably "sage -pip" install pytorch, theano, caffe, tensorflow, etc, within the sage environment. pytorch for instance installs very smoothly: http://pytorch.org/ ... but that wouldn't be very integrated. I don't think you should expect symbolic integration or group theory in the GPU for some time.

2018-01-29 08:08:22 -0600 commented question How can you change the viewpoint of perspective (to infinity) in a 3d plot?

That's related to the question:

https://ask.sagemath.org/question/384...

I don't know any simple way...

2018-01-28 16:35:35 -0600 commented answer Math document containing some Sage calculations

Is TeXmacs still alive? I loved that thing, but it is no longer in the ubuntu repos and I cannot install it from source. It looks abandoned.

2018-01-28 16:26:53 -0600 commented answer Math document containing some Sage calculations

Note that you must install rst2ipynb:

sage -i rst2pynb

Then you can use it

sage -rst2ipynb source.rst out.ipynb
2017-08-08 13:58:36 -0600 asked a question Can I generate 3D plots in isometric projection?

I'd like to show some plots in isometric projection. For certain plots, it's not hard to project the lines manually and do a 2d plot, but ideally, I'd like to rotate the plot with the mouse, and be able to show any 3d plot in isometric projection: do you know a way?

2017-04-28 10:38:04 -0600 answered a question Animation doesn't work

This code will display the animation embeded in a jupyter notebook

my_path = 'my.gif'
a.gif(savefile=my_path)
html('<img src="%s" />'%my_path)

Warning: this saves the animation in the same folder where the notebook is.

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2017-01-26 12:21:42 -0600 answered a question How does one use the qhull optional package?

I'll expand on tmonteil's last comment: there is an interface to qhull included on scipy!

For example, this code computes the hull of a random set of 2D points:

import numpy as np
from scipy.spatial import ConvexHull
points = np.random.rand(30, 2)   # 30 random points in 2-D
hull = ConvexHull(points)

and this code plots it:

my_plot = point2d(points)
for simplex in hull.simplices:
    my_plot += line2d([points[v,:] for v in simplex])
my_plot

While this code computes the hull of a random set of 3D points:

import numpy as np
from scipy.spatial import ConvexHull
points = np.random.rand(30, 3)   # 30 random points in 3-D
hull = ConvexHull(points)

and this code plots it:

my_plot = point3d(points)
for simplex in hull.simplices:
    my_plot += line3d([points[simplex[-1],:]]+[points[v,:] for v in simplex])
my_plot
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2016-10-26 12:15:41 -0600 commented question Using sage for slideshows/presentations

This thread is a bit old. These days the jupyter notebook has some reveal.js integration available when we use sage --notebook=jupyter. However it is not trivial to use. Should I ask for a sage tutorial for this feature here, or in a new question?

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2016-05-12 08:22:08 -0600 commented question qepcad failing to replicate examples

Can we mark this question as outdated? qepcad installs just fine, and I can think of no reason why anyone would want to read it now.

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2015-12-01 05:30:35 -0600 commented question elementary matrices for elementary row operations
2015-12-01 05:16:28 -0600 commented answer Reformulation of a semialgebraic set, without quantifiers

I had problems installing sage from source, but I finally did it, and qepcap installed without problems. Thanks again, Thierry!

2015-11-24 04:20:21 -0600 asked a question Convert sagews into sws

A colleague asked if it is possible to convert from sagews into sws, so that he can use the notebooks that his students create on Sage Cloud.

I have found a sage-cloud thread which mentions this quick script.

My motivations for writing this questions are:

  1. I thought ask.sagemath.org should have an answer to that question
  2. There will be better ways in the future
  3. There may be better ways now!

So feel free to contribute and keep this question up to date!


PD: For the record, sws files are compressed tar files that you can decompress with tar jxf %F. They contain an html file with code and comments, a pickle file with some python objects, a data folder with the attachments, and a cells folder with the images contained in the output of the cells. On the other hand, sagews files are plain text files with no attachments.

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2015-10-28 09:33:01 -0600 commented answer Reformulation of a semialgebraic set, without quantifiers

I do have a trac account. I'll try first with a fresh sage install. My current sage install is old, and has been updated several times. I'll need a few days: if it works I'll comment here, and if it doesn't I'll fill a bug. Regards!

2015-10-28 06:27:21 -0600 commented question Reformulation of a semialgebraic set, without quantifiers

For the record: I couldn't get qepcad to make a projection of codimension 2 using even 4 points, but I did get some significant results by restricting to a three dimensional space, so that qepcad only projects along lines.

2015-10-28 05:06:16 -0600 commented answer substitute expression instead of formal function symbol

f.operator() is actually foo.

2015-10-28 04:57:48 -0600 answered a question Difference of performance bewteen a core i5 and core i7?

If you plan to take exams and/or work with novices, I'd say it's worth it. It's not easy to jail each process and give it limited resources. If X students write an infinite loop, you server will collapse. The more threads and RAM you have, the greater X can get.

If you divide the available RAM into the total number of students, you're wasting resources, it's better to estimate the number of students that can write an infinite loop that appends to a list, and not hit interrupt and/or restart on time.

In my experience, the probability of a student blowing the server is higher on a exam than on a regular class, and it's higher in combinatorics or number theory, average on linear algebra, lower on calculus (unless the exercise involves symbolic integration of non-trivial functions).

2015-10-28 04:45:07 -0600 answered a question How can i set up a server that uses several computers?

Old question, but still: have you looked at the code from the Sage cloud:

https://github.com/sagemathinc/smc

The Sage cloud seems to be actually easier to install in several machines than in only one >:O !

2015-10-28 04:36:28 -0600 commented answer Reformulation of a semialgebraic set, without quantifiers

I have bug traces etc: should I open a ticket?

2015-10-28 04:26:32 -0600 marked best answer Reformulation of a semialgebraic set, without quantifiers

According to wikipedia:

The Tarski–Seidenberg theorem states that a set in (n + 1)-dimensional space defined by polynomial equations and inequalities can be projected down onto n-dimensional space, and the resulting set is still definable in terms of polynomial identities and inequalities.

That's great, and my question is if it can be done in practice, in a particular case. I have read that the original Tarski–Seidenberg algorithm is of little practical use, but maybe my problem is tractable with another algorithm:

We have a finite set of points in C^2 (z_i,w_i), and I want to project onto the first C coordinate the intersection of the cones {(z,w): |z-z_i|>|w-w_i|}. It would be awesome, for example for plotting the set, if I could actually get the polynomial inequalities that define the projection. Getting only the higher dimensional strata is fine (an open set in C).

Any idea? Thanks in advance.

2015-10-28 04:26:30 -0600 commented answer Reformulation of a semialgebraic set, without quantifiers

I get a "RuntimeError: unable to start QEPCAD". I upgraded to sage 6.9 with

./sage -upgrade

and I installed qepcad with

./sage -i qepcad

The first upgrade reported errors when building the html docs, but nothing else, and everything seems to work fine. The installation of qepcad produced no errors (I think), and there are qepcad and saclib folders in sage/pkgs.

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2015-10-27 10:31:11 -0600 commented answer Reformulation of a semialgebraic set, without quantifiers

It just finished installing. Thanks for taking care of this packege, Thierry!

2015-10-27 10:19:49 -0600 commented answer Reformulation of a semialgebraic set, without quantifiers

I downloaded the program and I'm calling it from the command line. I can't get it to work on any non-trivial example (it does work with all the examples from its documentation). The output is:

Failure occurred in: GCSI (final check) Reason for the failure: Too few cells reclaimed.

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2015-10-27 05:35:00 -0600 edited answer Reformulation of a semialgebraic set, without quantifiers

I found the optional package qepcad:

http://flask.sagenb.org/src/interface...

mentioned in this site:

http://mathoverflow.net/questions/159...

2015-10-27 04:31:05 -0600 commented question Similar command to Mathematica's Reduce[]?

I just found about the optional package qepcad:

http://flask.sagenb.org/src/interface... http://mathoverflow.net/questions/159...

maybe it works for you!