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2020-08-23 14:57:21 -0600 | answered a question | Obtaining quotient posets of the Boolean lattice via Sage Here is a snippet of code that can be used to produce the desired quotient poset. It is not meant to be the most optimal way, but it does return the desired object. To obtain all of the quotient posets, one should then loop over all permutation subgroups of $S_n$. These subgroups can be obtained this way: |

2020-07-28 05:14:55 -0600 | answered a question | rotating polytope in 4d? The current default viewer in Sage is now threejs. To visualize a 4-dimensional polytope, you can do: This will open a html page in the default internet browser (this might be a problem, as sometimes if the browser was updated it might not open a new tab). In there, there will be a threejs applet which you can play with with mouse-clicks. You are probably refering to the pop up menu from the jmol viewer, which is still accessible (though likely is less maintained now as it is not the default viewer anymore): There, you may right-click and select "console" where you can then type commands to rotate and change the view. As far as I know, there was no possibility to change the projection view (from 4d to 3d) once the picture of the Schlegel diagram has been produced. It is possible to change the projection view, for this, you may proceed to play around as follows: |

2020-07-24 02:41:57 -0600 | commented answer | Shelling order of a simplicial polytope Sure! If you want to keep track of the development related to polyhedral geometry in Sage visit the Polyhedral Geometry Trac Wiki. The .boundary_complex method is in Sage since version 9.0. |

2020-07-24 02:30:16 -0600 | answered a question | Shelling order of a simplicial polytope Dear Guillermo, The answer to your question is yes. Here is an illustration with the octahedron: Finally, we can get the actual sequence of facet using our dictionary. |

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2020-04-26 14:48:43 -0600 | marked best answer | How to literally print the output of tab completion in the command line? Some time ago, I realized that pressing tab after a "." in the command line opens a new window where it is possible to scroll through the possible methods to call on this object. Is it still possible to print inside the terminal all the possibilities? Even if I modify the preferences of the command line from "readline" to "multicolumns", it still does not show much of the possibilities and sometimes seeing all of them at once is faster than scrolling. Is it possible to get this feature back as before somehow? |

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2020-04-24 02:39:58 -0600 | commented answer | Projection along affine hull Perhaps you could complete this answer with the code to obtain P? |

2020-04-23 02:57:24 -0600 | commented question | Memory leak in Polyhedron? This memory leak in Polyhedron is fixed in this ticket. |

2020-04-23 02:48:39 -0600 | commented answer | Compute the centroid of a polytope ... which will be accessible with the command |

2020-04-23 02:43:49 -0600 | commented answer | plotting 5,8,16,24,120 and 600-cells The 120-cell is now available in the library. The |

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2020-04-08 10:08:58 -0600 | answered a question | PolyhedronFace In sage 9.0, I can execute: Which version of sage are you using? That might be a problem as the function |

2020-03-01 04:43:48 -0600 | commented answer | Find sphere points in a lattice I see. If it is in Sage I would suspect that it is closer to the number theory and quadratic forms code, but I am not aware of it... |

2020-02-13 03:30:16 -0600 | answered a question | looping of equality function Defining You do not need to declare the variables if you use them in a range: You can also use more advanced iterators and shorten the code: |

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2020-02-10 12:00:08 -0600 | answered a question | Find sphere points in a lattice Here is a snippet of code that should do: You will get a set The norm squared seem to deliver the same as the symmetric form: |

2020-02-10 06:47:43 -0600 | answered a question | VoronoiDiagram returns empty regions This looks like a bug. I have reported it on trac: ticket 29176 Thanks for reporting this! |

2020-02-10 06:41:12 -0600 | answered a question | Typo in Sage documentation (no. 2) This is now a ticket: ticket 29175 |

2020-02-07 12:08:19 -0600 | commented answer | Intersection of a Cube with two planes and resulting polyhedron In a more recent version you can do: |

2020-02-07 11:59:29 -0600 | commented question | hyperplane arrangements raises error on regions I would also try to use rational numbers instead of floats, this might facilitate the computations. You probably do not need floats, as the size of the input is reasonable. say |

2020-02-07 11:52:55 -0600 | commented question | Find sphere points in a lattice Could you explain what is meant by "canonical bilinear form", the one coming from the geometric representation? This will affect how to give you a better answer. |

2020-02-07 11:44:42 -0600 | commented question | Sage notebook only runs when a browser is already open With the notebook, it is also useful to restart the browser once in a while if an update was made (I rarely restart my browser and I was getting similar problems with start-up, restarting the browser did the thing...) Maybe try with have a freshly updated firefox, that does not run, and moving the .sage folder to another location and then so what happens? |

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2020-01-08 10:41:03 -0600 | answered a question | Lattices via sage Here is a first attempt to answer your questions. 1) The comment should be addressed in order to give an instructive answer. 2) Assuming you want to consider only _linear_ subspace, the following code does the thing: 3) See https://ask.sagemath.org/question/389... and https://ask.sagemath.org/question/389... |

2020-01-08 06:53:33 -0600 | commented question | Lattices via sage Could you clarify which lattice you mean? A lattice can be a subgroup of the additive group |

2019-10-26 04:49:16 -0600 | commented question | LattE problem: Executable 'count' not found on PATH. I also get 39 for the command As mentioned in the documentation obtained by typing I suspect that you are interested in the Ehrhart polynomial. It is important to know that counting the lattice points in a lattice polytope and obtaining the Ehrhart polynomial are two completely different tasks, although they are obviously related. |

2019-10-25 17:19:36 -0600 | commented answer | How to find the vertices a a polyhedron define by inequalities , It is also possible to get the full V-representation using the |

2019-10-25 17:17:43 -0600 | answered a question | Computing projection of a polyhedron One possibility is the following. First create the desired transformation as a matrix. Then, create your polyhedron One then just need to apply the transformation on each vertices of the polyhedron and take the result back to a polyhedron. Currently, projections (or other linear transformations) are not implemented better than as above... |

2019-10-25 13:12:07 -0600 | answered a question | About algorithm for testing whether a point is in a V-polyhedron You can access the algorithm for containment by doing the following: This will show you the source code for this function. The containment check is independent of the backend. Currently, when you create a polyhedron object in Sage, it computes the other representation (H- to V-, or V- to H-) automatically (this may change in the future, but for now, it is so). Then, checking containment is obtained directly from the H-representation by matrix multiplication and checking the equality or inequality of There is absolutely no difference between bounded vs unbounded polyhedron. To know if the function depends on the backend, you can look next to the 1-to-last line in the output of |

2019-09-14 00:56:10 -0600 | commented answer | jmol stuck at "Initializing 3D display" Thanks! That explains why it was stuck indeed. I did create a dummy worksheet to execute my snippet of code and jsmol does work inside jupyter notebooks. |

2019-09-12 03:49:13 -0600 | asked a question | jmol stuck at "Initializing 3D display" I have a freshly compiled version of sage 8.9.rc0. jmol used to work fine until I got it stuck at "Initializing 3D display" The pop out window opens and then is stuck for eternity. This is annoying. I know that I could use a different viewer like (I also upgraded my debian from stretch to buster, but I do not think it is the problem since jmol starts fine outside of sage) How to fix this? |

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2019-08-27 15:24:47 -0600 | answered a question | Computing the volume of a polytope that is not full-dimensional There is a simple way to do so directly in Sage: Naturally, it is lower dimensional, so its volume is zero: But, changing the The |

2019-08-27 15:04:46 -0600 | answered a question | Is it possible to compute the face lattice of a polytope from its vertex-facet incidences? From Sage version 8.9+, on, the class Here is an example with your suggested Egyptian pyramid: So far, there are a few things you can call on |

2019-08-27 09:21:01 -0600 | edited answer | Can sage compute the h* vector of a polytope? You can use the You can install them by typing: Then, in a terminal with Sage 8.9 or more recent, you can get the h^*-vector by typing: This hypercube is the ±1 cube, so its volume is Eventually, once this ticket is merged, it will be possible to call it directly on the polytope like so: |

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