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2011-06-29 08:36:52 -0500 | commented answer | Working with sage graphics I apologise for misleading you. I have done what you suggest. I have also written the code for plotting ribbon graphs. It works. For an individual ribbon graph it is slow. For a linear combination graphics_array works but is not really satisfactory. I have not tracked down the code for graph plotting. |

2011-06-29 07:07:06 -0500 | commented answer | Working with sage graphics I was asked to produce a toy example. Maybe I did not choose a good example. |

2011-06-29 04:44:08 -0500 | commented answer | Working with sage graphics I am aware of list comprehension. I don't see how this helps. |

2011-06-29 04:41:32 -0500 | commented answer | Working with sage graphics I am not explaining myself very well. I am implementing the mathematical notion of a ribbon graph. There is some overlap in the functionality with abstract graphs. I might learn something from the code for the sage Graph class but I can't just call the functions. |

2011-06-28 22:53:41 -0500 | commented question | Working with sage graphics Which graph plotting procedures are you referring to? |

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2011-06-28 01:02:28 -0500 | asked a question | Working with sage graphics I have written some code to plot some graphs (that is vertices and edges) and it has been suggested that I am being inefficient. I have say 50-100 primitives (consisting of lines and circles). At the moment I use to Graphics() to create an empty graphics object and then use + to add the primitives. Is there a better way to do this?
A second question is that I would also like to plot a formal linear combination of these graphs. At the moment I produce a list with a graph and the coefficients (via latex) alternating and then use graphics_array(). However I would prefer to group the primitives in a graph and in the latex and then scale these and place them myself.
I have looked at the matplotlib home page. I can see that there is a class Figure and so on. Should I be attempting to use these since I am working in sage? I have used metapost and tikz in the past but not matlab. P.S. I tried g=DiGraph() g.plot? and was directed to a file decorators.py |

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2010-09-03 05:13:32 -0500 | answered a question | Structure constants for unitary groups I suspect that you have not had a response because your question is not clear. First of all from the expression you give it looks as though you want the structure constants of a Lie algebra. Secondly the cross product of vectors in 3D gives the Lie algebra of SO(3) or SU(2). The Lie algebra of SU(3) has dimension 8. Your question asks for the definition of the structure constants which is a mathematical question. If you are asking a mathematical question you would be better off on another site, probably http://math.stackexchange.com/. If you are asking about an implementation in sage you should be clear about the mathematics. |

2010-09-02 22:29:19 -0500 | commented answer | Using CombinatorialFreeModule Jason, This seems to do what I want. Thanks for your help. |

2010-09-02 21:01:04 -0500 | marked best answer | Using CombinatorialFreeModule Here is a minimal example that may do what you want: Here is how to use this with CombinatorialFreeModule: |

2010-09-01 07:48:17 -0500 | commented answer | Using CombinatorialFreeModule I agree that Parents and Elements will come into this. I have tried reading the documentation on Categories and I have simply not grasped the idea. |

2010-09-01 06:54:19 -0500 | commented answer | Using CombinatorialFreeModule My class does not have addition and multiplication. This is purely formal (as in, for example, the group algebra of a group which may be infinite). |

2010-09-01 06:53:00 -0500 | commented answer | Using CombinatorialFreeModule The examples in the documentation give finite lists. I require the (potentially) infinite set of all instances of a class. |

2010-09-01 00:30:58 -0500 | asked a question | Using CombinatorialFreeModule Could I please have some help on using CombinatorialFreeModule? I have looked at the documentation and the only examples are free modules on a finite set. I have designed my own class and I now want to work with linear combinations of instances of the class. I have been told that one issue is that instances have to be immutable (so they can be hashed?). The attributes of my class are all integers and tuples (of integers). However I am not sure if this is sufficient. Let's say I have defined a class G whose attributes are all integers and tuples. Then the idea would be say M = CombinatorialFreeModule(QQ,G) to define the free module on instances of G with rational coefficients. Then if g,h,k are instances of G I would hope to be able to put say a = (2/3) For example, a simple (but inefficient) way to calculate the chromatic polynomial of a graph would be to use contraction/deletion. This starts with a graph and finishes with a polynomial but the intermediate stages are formal linear combinations of graphs. Similarly the skein relation approach to link polynomials has intermediate stages which are formal linear combinations of link projections. |

2010-08-19 10:14:06 -0500 | asked a question | Quantum binomials What is the difference between |

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