Rank: 200 based on 494 downloads (last 30 days) and 17 files submitted
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Tristan Ursell

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Company/University
Stanford University

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Professional Interests:
physics, biophysics, genetic algorithms

 

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Files Posted by Tristan View all
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(last 30 days)
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17 Oct 2014 Screenshot Generate Random Numbers from a 2D Discrete Distribution Random numbers from any 2D discrete probability distribution, at any resolution. Author: Tristan Ursell discrete, distribution, generate, noise, number, probability 59 3
  • 5.0
5.0 | 2 ratings
08 Nov 2013 Screenshot Active Figure Zoom for Selecting Points Select points at a user-specified zoom level that moves around the image as you click. Author: Tristan Ursell figure, zoom, select, points, line, ginput 26 0
29 Oct 2013 Screenshot Adaptive Colormap Function Creates a Colormap Specific to Data Easily design and fit a colormap to the values in your data! Author: Tristan Ursell color, red, blue, green, colormap, map 18 3
30 Sep 2013 Connect Randomly Ordered 2D Points into a Minimal Nearest-Neighbor Closed Contour Connects randomly ordered 2D points into a minimal nearest neighbor contour. Author: Tristan Ursell contour, nearest, neighbor, 2d, point, points 36 15
  • 4.5
4.5 | 5 ratings
09 Jul 2013 Screenshot 1D Non-derivative Peak Finder Up-sample and filter noisy data to find peaks without using derivatives. Author: Tristan Ursell signal processing, interpolation, measurement, peak, location, finding 49 5
  • 5.0
5.0 | 2 ratings
Comments and Ratings by Tristan View all
Updated File Comments Rating
17 Oct 2014 Generate Random Numbers from a 2D Discrete Distribution Random numbers from any 2D discrete probability distribution, at any resolution. Author: Tristan Ursell

Good catch -- I just put a check in the code to make sure the interpolated values are always positive.

17 Oct 2014 Connect Randomly Ordered 2D Points into a Minimal Nearest-Neighbor Closed Contour Connects randomly ordered 2D points into a minimal nearest neighbor contour. Author: Tristan Ursell

@Frank -- That's an interesting idea, but I worry that it's too dependent on which point you choose as the first point. In other words, for the same vector, different starting points would give different results (although the same is true for the algorithm in general). Probably the right way to do something like that is calculate a distance matrix for all points and then do a bit of graph theory to group the points by mutual distance. Give it a try :)

26 Oct 2013 Adaptive Colormap Function Creates a Colormap Specific to Data Easily design and fit a colormap to the values in your data! Author: Tristan Ursell

Hey Blake -- found the single character bug that caused this! Be careful with the "<" vs. "<=" :)

29 Sep 2013 Connect Randomly Ordered 2D Points into a Minimal Nearest-Neighbor Closed Contour Connects randomly ordered 2D points into a minimal nearest neighbor contour. Author: Tristan Ursell

Zheng -- found a small bug that was responsible. New version uploaded, and awaiting approval from Mathworks (or just add "bad_pts=zeros(size(Xin));") at line 235. Thanks!

29 Sep 2013 Connect Randomly Ordered 2D Points into a Minimal Nearest-Neighbor Closed Contour Connects randomly ordered 2D points into a minimal nearest neighbor contour. Author: Tristan Ursell

Hi Zheng, I presume this was with the last example? I'll take a look.

Comments and Ratings on Tristan's Files View all
Updated File Comment by Comments Rating
17 Oct 2014 Generate Random Numbers from a 2D Discrete Distribution Random numbers from any 2D discrete probability distribution, at any resolution. Author: Tristan Ursell Ursell, Tristan

Good catch -- I just put a check in the code to make sure the interpolated values are always positive.

17 Oct 2014 Connect Randomly Ordered 2D Points into a Minimal Nearest-Neighbor Closed Contour Connects randomly ordered 2D points into a minimal nearest neighbor contour. Author: Tristan Ursell Ursell, Tristan

@Frank -- That's an interesting idea, but I worry that it's too dependent on which point you choose as the first point. In other words, for the same vector, different starting points would give different results (although the same is true for the algorithm in general). Probably the right way to do something like that is calculate a distance matrix for all points and then do a bit of graph theory to group the points by mutual distance. Give it a try :)

01 Oct 2014 Generate Random Numbers from a 2D Discrete Distribution Random numbers from any 2D discrete probability distribution, at any resolution. Author: Tristan Ursell S, M

Excellent code, and amazingly, the only FEX submission for random sampling from 2D distributions.

I did run into a little bug. When using interpolation (res>1), I occasionally get "Error: All elements of first argument, P, must be positive." thrown by gendist(). This looks like it comes from interpolation giving negative numbers. The only hint at the culprit is that the joint PDFs I'm sending to your function have very very small numbers, (e.g., 1.4822e-323). When more reasonable numbers are used, the interpolation is fine.

23 Aug 2014 Connect Randomly Ordered 2D Points into a Minimal Nearest-Neighbor Closed Contour Connects randomly ordered 2D points into a minimal nearest neighbor contour. Author: Tristan Ursell Pennekamp, Frank

Hi,
This is a great function you've made here! But I was wondering if it is possible to find multiple closed contours in one X and Y vector?

maybe using an if statement when the starting point is closer than any other data point it closes the contour and starts a new one on the next point of your vector?

I think this would be a very nice addition to your program for when your working with big spatial datasets.

Cheers

30 Jan 2014 Frechet Distance Calculator Estimate the similarity between curves in space using the scalar Frechet Distance. Author: Tristan Ursell R, Venkat

Nice submission. Has great potential application.

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