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Darren Rowland

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Files Posted by Darren Rowland View all
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08 Nov 2010 Screenshot diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland derivative, differentiation, gradient 43 4
  • 5.0
5.0 | 4 ratings
05 Aug 2009 Puzzler: solution Solver for the puzzler posted by Doug Hull July 09 http://blogs.mathworks.com/videos/ Author: Darren Rowland algorithm, flood, puzzler 7 0
27 Apr 2009 FACTORADIC Obtain the factorial radix representation of a number. Author: Darren Rowland factoradic, factorial radix, lehmer code, permutation 10 1
  • 5.0
5.0 | 1 rating
22 Feb 2009 ONEPERM Obtain a single permutation of the numbers 1:N Author: Darren Rowland single permutation 3 1
22 Feb 2009 ONECOMB Obtain a single combination of N numbers taken K at a time. Author: Darren Rowland single combination, combinadic 6 4
  • 5.0
5.0 | 3 ratings
Comments and Ratings by Darren Rowland View all
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27 May 2013 Logistic curve fit Fit a time series to a best-fitting logistic function. Author: James Conder

Hey James,

I've tested out the new code and it works a lot better for my case. One problem I've now identified is that you are not re-reversing t at the end of the function, so the calculated Qpre can be in error.

Other than this, I would suggest for you to include a brief usage example within the Help comments, e.g. constructing data from known parameters, adding some random error and obtaining parameter estimates. Just a few lines to help someone getting started.

Also, you should turn the various plotting calls off by default then have an extra (optional) input parameter for people to use to turn them on.

Hope that helps,
Darren

22 May 2013 Logistic curve fit Fit a time series to a best-fitting logistic function. Author: James Conder

Hi James,

This is a nice function but there is a failure condition to be aware of.

When I run the function on the following data, Qpre = 169.35 for all t. However, if I multiply t by 100, the function returns a better result.

Perhaps you can detect these cases and scale the vector internally to correct.

Darren

t = [0.8753
0.9267
0.9499
0.9678
0.9875
1.0206];
Q = [ 48.3871
96.7742
145.1613
193.5484
241.9355
290.3226];

30 May 2011 Functions that checks if a number is odd or even Determine if a number is odd or even. Works with floats and integers. Error checking. Author: Ulf Carlberg

Hi Ulf,

I notice that there are a couple of other FEX files called "isodd".
http://www.mathworks.com/matlabcentral/fileexchange/24278
http://www.mathworks.com/matlabcentral/fileexchange/2006

Do you know of any differences between these files and yours?
Darren

18 Nov 2010 diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland

@ Carlos,
Yes this will handle equally spaced data too. The formula I have used reduces to the central difference formula when the data are equally spaced, so the result is mostly the same as GRADIENT in that case.
The first example in the file demo_diffxy demonstrates the case of equally spaced points (follow the link next to 'Published MATLAB Files' above to view).
Darren

11 Aug 2010 Alopex-DE algorithm using the Alopex-DE algoritht to solve dynamic optimization Author: fan qinqin

This submission can't be used in its current form as it appears to be missing some functions.
There are also 44 M-lint messages, mostly relating to variables which are set but never used.

Comments and Ratings on Darren Rowland's Files View all
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07 May 2014 diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland Maarten

Hi Darren,

Great script you have here. Do you have any ideas where i can find some more information about the differentiation algorithm you are using?

thanks

07 May 2014 diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland Maarten

20 Mar 2014 diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland Philip Ohnewein

29 Jan 2014 diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland Philip Ohnewein

Tested it for 1-dimensional data only: Easy to use, does exactly what it is expected to do. Thank you very much!

18 Dec 2013 ONEPERM Obtain a single permutation of the numbers 1:N Author: Darren Rowland Peter Li

Ah, based on recursive permutation as here: http://www.mathworks.com/matlabcentral/fileexchange/13060-perms1

So not in the same order as Matlab PERMS or C++ STL NEXT_PERMUTATION. I guess this means I can't use this as starting points for a multithreaded version based on STL.

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