ZankerH comments on Open Thread April 11 - April 17, 2016 - Less Wrong

3 Post author: Clarity 10 April 2016 09:01PM

You are viewing a comment permalink. View the original post to see all comments and the full post content.

Comments (145)

You are viewing a single comment's thread. Show more comments above.

Comment author: DataPacRat 11 April 2016 09:03:22PM 1 point [-]

Welp, it looks like it's been longer since I tried tweaking basic code than I thought. I'm having trouble just trying to adjust the box's range to be from -124 to -71 and 25 to 53 (ie, longitude and latitude) instead of 1-10/1-10. I'm going to keep puzzling away, but anyone reading this, feel free to offer advice. :)

(I have some TV to watch later with the fam, so I won't mind doing some drudge work during the shows of typing out the city-list into an array of X/Y coordinates and population/weight, to paste into the Python script in place of randomly-generated points. ... Once I figure out how to get the script to accept a fixed array instead of randomly-generated points.)

Comment author: ZankerH 11 April 2016 10:02:38PM 3 points [-]

The range is specified by the box argument to the compute_2d_voronoi function, in form [[min_x, max_x], [min_y, max_y]]. Points and weights can be specified as 2d and 1d arrays, e.g., as np.array([[x1,y1], [x2, y2], [x3, y3], ..., [xn, yn]]) and np.array([w1, w2, w3, ..., wn]). Here's an example that takes specified points, and also allows you to plot point radii for debugging purposes: http://pastebin.com/h2fDLXRD

Comment author: DataPacRat 11 April 2016 10:57:36PM 1 point [-]

Thank you kindly for your help so far. :)

I started entering the live city data, and everything was going fine. Had to tweak the weights a bit to avoid some initial problems... then I got to Washington DC, and nothing I try seems to get it to work again. http://pastebin.com/q1JhUpSp is what I've ended up with; if I comment out DC's lines, I get a plot, if I put it back in, python just errors out, no matter what I set the weight divisor to. Any thoughts?

Comment author: ZankerH 11 April 2016 11:25:08PM *  3 points [-]

Two things:

  • all other points have a negative x coordinate, and the x range passed to the tessellation algorithm is [-124, -71]. You probably forgot the minus sign for that point's x coordinate.

  • as mentioned above, the algorithm fails to converge because the weights are poorly scaled. For a better graphical representation, you will want to scale them to the range between one and one half of the nearest point distance, but to make it run, just increase the division constant.

Comment author: DataPacRat 11 April 2016 11:57:06PM 2 points [-]

You probably forgot the minus sign

<forehead slap>