Han's profile - activity

This Forum is really good. But how about to make Sage a formal community in Stack Exchange so that more people can know about Sage. So please join Sage currently informal community here, and be active.

Some times I have to solve large scale linear programming where the the constraints are given in matrix. However, all tutorials provided only demonstrate very small scale cases. What if I have a linear programming given in a 1000*400 matrix. How to solve such a linear programming in Sage? Do I need to use another package to solve such linear programming problems?

I have Sage 6.3 installed on OS X 10.9. I can launch Sage without any problem. However, when I tried to launch Sage with options in terminal, it always launchs Sage notebook in safari. For example, if I type $ sage -v, Sage notebook opens; if I type $ sage -ipython notebook, Sage notebook opens again. What should I do to solve this problem? I'm new to sage and python, so forgive me for my ignorance。

Thanks for your answer. Looking forward to the problem being fixed.

I have Sage 6.4 and Mathematica 10 installed on my computer. I was trying to call Mathematica functions from Sage in terminal. Sage starts properly in terminal, but it hanged every time when mathematica() was called. By the way, I can start Mathematica kernel by calling math in command line. I have no idea why it doesn't work. Please help me out.

Some of my programs take hours to run. Can I close the tab and check the result later?

I was trying to plot the graphs of $K_6$ via code: g=graphs.CompleteGraph(6);g.plot().

However, the graph it returned is obviously not $K_6$. What's wrong with my code?

By the way, I'm working on .sagews in SMC. The weird thing is that I can draw the graph correctly in my local worksheet.

Thank you for the explanation. It's really helpful.

Thank you so much. I didn't know the function `integral_points()`. Just defining a new polyhedron on the integral points gives rise to the desired integer hull.

I'm trying to generate the matching polytope for general graphs by using MixedIntegerLinearProgram and Polyhedron.

Generally, starting with the incidence matrix of a given graph $G$, I can accomplish this task by either setting variables in MixedIntegerLinearProgram to be binary or adding the odd set constraints to MixedIntegerLinearProgram.

But now I'm trying to get the matching polytope by simply taking the Integer Hull of the polytope defined by incidence matrix of $G$ without setting variables to be binary or adding the odd set constraints to MixedIntegerLinearProgram.

So is there a integer_hull function in sage or how can I get the integer hull from a given convex hull?

Is it possible to call Sage functions from Mathematica?

I'm new to Sage. I find that some functions in Sage are extremely useful for me. But I'm not so used to the language in Sage. Instead, Mma is currently my main tool. So I wonder whether I can call Sage functions from Mathematica.

@tmonteil Thank you so much for your suggestions. It is really helpful. The function you mentioned above G.subgraph_search() together with function minor() found by following @dazedANDconfused 's instruction are exactly what I need in my research. Thank you guys for your patient explanations.

@dazedANDconfused Thank you so much for sharing. I checked the pages you mentioned above, and it is really helpful, especially two functions concerning minors.

Is it possible to generate random graphs free of certain forbidden structures? For example, graphs without $C_3$.

Or is it possible to test whether a graph is free of some forbidden structures?

If it is positive, then it would be of great help in my research. Looking forward to all comments and suggestions.

I'm afraid the code cannot return what I expected. Yes, it returns a Wheel graph with 15 vertices. But the graph drawn there is ugly. Thank you for sharing anyway.

I have the same question here. Hope there is a way to solve it.

I was trying to plot some graphs in SMC. However, even the first example given in Graph Plotting doesn't work. I only got an empty output. The following is the example i was trying.

sage: G = graphs.WheelGraph(15)

sage: G.plot()

What am I missing in my example?

P.S.: Yes. The example works in Sage worksheets, however, it doesn't work in iPython notebook. How to make it work in iPython notebook?