Rank: 495 based on 277 downloads (last 30 days) and 3 files submitted
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Richard Brown

E-mail
Company/University
Massey University
Lat/Long
-40.3864, 175.6187

Personal Profile:

Maths Lecturer at Massey University. Working on high performance computing and modelling.

Professional Interests:
numerical analysis, modelling, computer vision, mathematical biology

 

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Files Posted by Richard View all
Updated   File Tags Downloads
(last 30 days)
Comments Rating
07 Sep 2007 Screenshot nearestneighbour.m Computes nearest neighbour(s) by Euclidean distance Author: Richard Brown nearest, neighbor, neighbour, closest, delaunay, dsearch 104 5
  • 5.0
5.0 | 3 ratings
29 May 2007 Screenshot fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown approximation, interpolation, least squares, ellipse, fit, conic 110 22
  • 4.71429
4.7 | 7 ratings
21 May 2007 Screenshot fitcircle.m Fits circles to 2D data using nonlinear least squares to minimise geometric error Author: Richard Brown approximation, interpolation, fitcircle, least squares, circle, gauss newton 63 16
  • 4.6
4.6 | 5 ratings
Comments and Ratings by Richard View all
Updated File Comments Rating
04 Mar 2013 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown

@leon, not directly. It fits ellipses to pairs of points that are assumed to represent the ellipse boundary. So, you need to segment your images first, then extract the boundary points and fit the ellipse to those.

07 Sep 2012 fitcircle.m Fits circles to 2D data using nonlinear least squares to minimise geometric error Author: Richard Brown

@Tolga, thanks -- and yes, I know. I deliberately wanted to avoid any toolbox dependencies.

I haven't done any comparisons of efficiency -- if you do you could let us know! But accuracy is simply dependent on the tolerance you specify.

28 Jun 2012 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown

@Irfan: x and y values!

21 May 2012 fitcircle.m Fits circles to 2D data using nonlinear least squares to minimise geometric error Author: Richard Brown

My previous comment got lost -- the 2 norm residual is the sum of the squared perpendicular distance from each data point to the fitted circle

21 May 2012 fitcircle.m Fits circles to 2D data using nonlinear least squares to minimise geometric error Author: Richard Brown

Also, @Graeme, the accuracy of the fitted circle depends on the kinds of errors that are in your data. If you assume there is a true underlying set of parameters that you're trying to find, and that your data is normally distributed, then the accuracy will decrease with number of data points as something like s / sqrt(n), where s is the standard deviation of perpendicular distances to the fitted circle, and n the number of data points. The error will then probably follow some kind of t distribution.

Comments and Ratings on Richard's Files View all
Updated File Comment by Comments Rating
02 Mar 2014 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown Manuela

Hello Richard, if I want to use the 'a' and 'b' values given by this program to find the area of the ellipse what would be the units of the area? Pixels perhaps?

13 Feb 2014 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown Ross

Hi Richard, thank you for this code. Quick question: how can I estimate the error of the fit? Something like an R-value... Thank you!

05 Nov 2013 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown K

Hello,

This code was exactly what I was looking for to fit ellipses to a set of data points (hysteresis loops). I may have some questions in the future, but for now, thanks!

23 Aug 2013 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown Georgi

Hello,
First of all, my compliments about this work-excellent!
I am trying to write the code and have some questions because i am beginner with matlab.When i try to declare the function(function [z, a, b, alpha] = fitellipse(x, varargin)) i become an error like this:
Error: Function definitions are not permitted in this context.
Without this later i can't use the function because it isn't defined~!
I would be gratefull if you help me,because i really need this.

Thanks in advance

05 Mar 2013 fitellipse.m Fit ellipses to 2D points using linear or nonlinear least squares Author: Richard Brown leon

Richard Brown,
how to segment the images?

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