Rank: 2671 based on 16 downloads (last 30 days) and 5 files submitted
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Darren Rowland

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08 Nov 2010 Published MATLAB Files diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland derivative, differentiation, gradient 15 2
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 0 0
27 Apr 2009 FACTORADIC Obtain the factorial radix representation of a number. Author: Darren Rowland factoradic, factorial radix, lehmer code, permutation 0 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 0 0
22 Feb 2009 ONECOMB Obtain a single combination of N numbers taken K at a time. Author: Darren Rowland single combination, combinadic 1 3
  • 5.0
5.0 | 2 ratings
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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.
01 Jun 2010 Unique Random Integer List A simple function that produce unique random Integer List Author: Ibraheem

You can achieve the same behaviour with the function randperm too
10 Mar 2010 samplepick pick a random sample out of an array Author: Mauro

The function randperm is practically ready-made for this application. To draw a subset, s, of size m from a dataset, d, of size n, one can simply do

perm = randperm(n);
s = d(perm(1:m));
Comments and Ratings on Darren's Files View all
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18 Nov 2010 diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland Rowland, Darren

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

I noticed that you specified that this file was made to handle unequally spaced data but, I was wondering if it can also handle equally spaced data? Thank you.
24 Mar 2010 ONECOMB Obtain a single combination of N numbers taken K at a time. Author: Darren Rowland Aldahiyat, Husam

Very useful submission, well written.
16 Jan 2010 ONECOMB Obtain a single combination of N numbers taken K at a time. Author: Darren Rowland Campbell, Rob

This well coded and does what it says. Can be substantially faster than nchoosek. For example:

>> tic, for i=1:1E4;onecomb(10,5,5);end,toc/1E4
ans =
   7.3127e-05
>> tic, for i=1:1E4;NCHOOSEK(1:10,5);end,toc/1E4
ans =
   3.7945e-04

The 1 star review seems to have missed the point.
15 Dec 2009 ONECOMB Obtain a single combination of N numbers taken K at a time. Author: Darren Rowland Rowland, Darren

@ Marco/PXlab

It is exactly correct that this function with call structure

C1 = onecomb(N,K,M)

returns the same result as

AC = nchoosek(N,K);
C2 = AC(M,:)

The advantage of this function is that the intermediate array AC is not computed by ONECOMB. The array AC can be immensely large for large N and K approx N/2, and is a waste to compute if one only requires a small number of combinations from the total.

Additionally, if one requires many combinations, my testing (not included here but simple to duplicate) showed that the time to compute all the combinations using NCHOOSEK was approximately the same as computing all the combinations one-at-a-time using ONECOMB.
Top Tags Applied by Darren
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algorithm, combinadic, derivative, differentiation, factoradic
Files Tagged by Darren View all
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Updated   File Tags Downloads
(last 30 days) 		Comments Rating
08 Nov 2010 Published MATLAB Files diffxy Second-order accurate numerical differentiation (N-dimensional) Author: Darren Rowland derivative, differentiation, gradient 15 2
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 0 0
27 Apr 2009 FACTORADIC Obtain the factorial radix representation of a number. Author: Darren Rowland factoradic, factorial radix, lehmer code, permutation 0 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 0 0
22 Feb 2009 ONECOMB Obtain a single combination of N numbers taken K at a time. Author: Darren Rowland single combination, combinadic 1 3
  • 5.0
5.0 | 2 ratings

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