Matthew Roughan
 
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Various bits of code that may be useful to people:

  • AutoNetKit (ANK)
  • Matlab (most of this is also hosted on Matlab Central)
    • crosshatch_poly.m lets you do lines to fill a convex polygon (rather than filling the polygon with a flat color using the Matlab fill.m function. For instance see the following picture

      which was generated using crosshatch_poly_test.m.
    • plot_feasible.m is a simple bit of code for visualizing 2D linear programming problems. Its primarily of use for teaching Linear Algebra. It generates pictures of the form of
      which was generated using plot_feasible_test.m, though there are many options that can be used to alter the output. Note it uses the optimization toolbox, though this can probably be removed in the future.
    • ipf.m does Iterative Proportional Fitting (IPF). There are a couple of ways to use IPF, but in this case the aim is to find a matrix close to the input T that satisfies contraints on its row sums and column sums (its marginals). In particular we aim to find S with row sums equal to R, and column sums equal to C. To see how to use it have a look at ipf_test.m. More information can be found at Wikipedia or various other places on the web.

      There is a second version of this code used in our traffic matrix work, which is designed to allow one to find a matrix S that satisfies an arbitrary set of linear constraints y=Ax on a vectorized version x of the matrix T. Its not quite in a nice form to hand out, but it you need it ask me.
    • gaussian_mixture_model.m does simple 1D Gaussian Mixture Model estimation using the EM algorithm. It uses a couple of little functions for estimating Gaussian distributions, so best to grab the zip file. The result is that we can break a multimodal distribution such as displayed below into a random mixture of Gaussians.
    • randp.m generates Pareto random variables (of type I). The Pareto distribution is a classic heavy-tailed or power-law distribution. See "Statistical Distributions", Evans, Hastings and Peacock, Wiley, 1993 or my distributions page or Wikipedia for more information. For an example see the following generated using randp_test.m
    • rand_gamma.m generates Gamma random variables -- see "Statistical Distributions", Evans, Hastings and Peacock, Wiley, 1993 or my distributions page or Wikipedia for more information. For an example see the following generated using rand_gamma_test.m. Of course Matlab's stats toolbox has gamrnd which also does this, but not everyone has the stats toolbox.
    • Conversion routines to take a surface (a function z of (x,y) or (theta,r)) and convert this into a solid; much as meshz does, but a little more useful for outputting as an STL for frabrication in a 3D printer. There are two cases, one in Cartesian co-ordinates, and the other in polar co-ordinates. Plus two sets of examples to show how they are used.
      • If you want to print out the solids in STL format, then use surf2stl.m by Bill McDonald, which can be had from Matlab central. Examples of printing to STL are included in the examples above.
    • Reuleaux triangle code: A Reuleaux triangle is a shape of constant width. That means it can be used as a roller (but not a wheel) as the animation shows. It's not actually a triangle, but its based on an equilateral triangle. It's actually one of many such shapes and the code here provides some matlab functions for creating these shapes, and manipulating them.

      One of the trickiest things to do with such a triangle is that by rotating it around a non-fixed center, one can carve an approximate square, making a drill bit to drill a square hole (or nearly square) possible. The second animation shows this in action.

      There's more info in the zip file, along with examples of what you can do, including the animations.



      A more recent one showing a square drill animation based on a right-angled isoceles triangle. It shows that a point on the new rotor follows a square path exactly. Code to come.

    • Some useful bits of networking code: to come
    • Traffic matrix generation: to come
    • IGP weight generation: to come
  • Perl
    • Traffic decomposition code. to come

Matthew Roughan

Last modified: Wed Apr 27 14:34:00 2011