Rank: 5558 based on 1 downloads (last 30 days) and 3 files submitted

Helen Chen

E-mail: helen.chen@mathworks.com
Lat/Long: 42.300304, -71.34995

Personal Profile:: I am currently a member of the MATLAB Central team. I work with other MATLAB Central Team members to develop our community and our community site to better serve our members. If you have questions or comments about our site or our community, please drop me a note.
Professional Interests:: online communities, collaborative technologies

Watch this Author's files

Files
Watch Lists

Files Posted by Helen					View all 1 - 3 of 3
Updated		File	Tags	Downloads (last 30 days)	Comments	Rating
17 Jul 2009		File Exchange 2.0: Find a File Finding good files will (hopefully) be a lot easier with the new File Exchange. Author: Helen Chen	video, fex, fx, walkthrough, file exchange, tutorial	0	5
19 May 2009		File Exchange 2.0: Find an Author There are many new ways to find the people that make the File Exchange what it is today. Author: Helen Chen	video, file exchange, fex, fx, walkthrough, tutorial	0	4	5.0 5.0 \| 1 rating
18 May 2009		File Exchange 2.0: Submit a File Video walkthrough of how to submit a file on the new File Exchange Author: Helen Chen	video, file exchange, fx, walkthrough, screencast, tutorial	1	2

Comments and Ratings by Helen		View all 1 - 2 of 2
Updated	File	Comments	Rating
19 Aug 2011	Carrier & Symbol Timing Recovery This model implements a contemporary symbol timing recovery scheme. Author: Dick Benson	@Yang - Have you tried clicking on the "Download all" button at the top right of this page?
29 Oct 2008	File Exchange 2.0: Find an Author There are many new ways to find the people that make the File Exchange what it is today. Author: Helen Chen	Thanks Matthew! This is helpful. :-)

Comments and Ratings on Helen's Files			View all 1 - 5 of 10
Updated	File	Comment by	Comments	Rating
30 Apr 2010	File Exchange 2.0: Submit a File Video walkthrough of how to submit a file on the new File Exchange Author: Helen Chen	isakson, per	I cannot find a guideline for updating an existing submission. Is there any? Where do I enter the text that goes into the Updates box? / per
30 Oct 2008	File Exchange 2.0: Find an Author There are many new ways to find the people that make the File Exchange what it is today. Author: Helen Chen	Oliphant, Matthew	See, now I would have only given myself 4 stars as I had a bad cold when I did these. But I am glad you, and hope others, found them helpful.
29 Oct 2008	File Exchange 2.0: Find an Author There are many new ways to find the people that make the File Exchange what it is today. Author: Helen Chen	Chen, Helen	Thanks Matthew! This is helpful. :-)
23 Oct 2008	File Exchange 2.0: Find an Author There are many new ways to find the people that make the File Exchange what it is today. Author: Helen Chen	Oliphant, Matthew	Someone had trouble playing these file properly. If you experience an issue with the file, here's a direct link to a Codec that should fix any issues: http://www.techsmith.com/codecs/tscc/default.asp
23 Oct 2008	File Exchange 2.0: Submit a File Video walkthrough of how to submit a file on the new File Exchange Author: Helen Chen	Oliphant, Matthew	Someone had trouble playing these file properly. If you experience an issue with the file, here's a direct link to a Codec that should fix any issues: http://www.techsmith.com/codecs/tscc/default.asp

Top Tags Applied by Helen	1 - 5 of 38
file exchange, video, fx, screencast, tutorial

Files Tagged by Helen					View all 1 - 5 of 16
Updated		File	Tags	Downloads (last 30 days)	Comments	Rating
27 Sep 2010		Get HTML Table Data into MATLAB Identify tables and interactively select the data to bring into MATLAB. Author: Jeremy Barry	html, table, import, cell array, data, regexp	70	8	3.85714 3.9 \| 8 ratings
26 Jul 2010		Generate figures for Cleve's Corner on Compressed Sensing Demonstration of compressed sensing. Author: Cleve Moler	cleves corner, l1 magic, compressed sensing, resconstruction	53	1	5.0 5.0 \| 1 rating
16 Jan 2010		IMPLEMENTATION OF ECONOMICAL DISPATCH (DISTRIBUTION OF LOAD BETWEEN UNITS WITH IN A PLANT) IN MATLAB IMPLEMENTATION OF ECONOMICAL DISPATCH (DISTRIBUTION OF LOAD BETWEEN UNITS WITH IN A PLANT) IN MATLAB Author: Hafiz Kashif Khaleel	economical dispatch, plant, distribution of load, matlab, university of south a...	30	0	4.0 4.0 \| 1 rating
16 Jan 2010		Newton Raphson Power Flow Solution using MATLAB this is the general program for Newton Raphson solution. Author: Hafiz Kashif Khaleel	matlab, newton raphson power ..., power system operatio..., pso	75	0	4.5 4.5 \| 2 ratings
25 Sep 2009		Tromino Can you fill the 4x4 Checker Board with set of L-Shaped Trominoes??? Author: Krishna Lalith	fun, tromino, game, lshape, induction, modulo	2	0

Currently Watching
Type	Description
Author	Helen Chen
File	N-dimensional sparse arrays
Search	tag:contest

Files Matching Helen's Watch List					View all 1 - 5 of 37
Updated		File	Tags	Downloads (last 30 days)	Comments	Rating
21 Jan 2012		N-dimensional sparse arrays Creates an N-dimensional sparse array object, for arbitrary N. Author: Matt J	sparse, ndimensional, multidimensional, oop, reshape	36	34	4.0 4.0 \| 4 ratings
08 Nov 2011		solver-contest Fall 2011 Contest: Vines Author: amay	contest	0	0
07 Nov 2011		MATLAB Contest - Vines (Improved visualization tools) This is a modified version of the visualizevines.m and runcontest.m files that better shows the data Author: Alan Chalker	contest	0	1
01 Nov 2011		MATLAB Contest - Vines All the files needed to develop and score an entry for the MATLAB® Programming Contest. Author: The MATLAB Contest Team	contest	6	0	5.0 5.0 \| 1 rating
25 Apr 2011		MATLAB Contest - Crossword Puzzle All the files needed to develop and score an entry for the MATLAB® Programming Contest. Author: The MATLAB Contest Team	contest	7	3	5.0 5.0 \| 1 rating

Comments and Ratings Matching Helen's Watch List			1-5 of 35
Date	File	Comment by	Comments	Rating
26 Nov 2011	N-dimensional sparse arrays Creates an N-dimensional sparse array object, for arbitrary N.	Matt J	@Jens: Incidentally, if you are now happy with the reimplementation I've made of the DISPLAY method, I would appreciate it if you would change your rating. One star out of five is, in any case, a harsh rating just because you don't like 1 out of the 92 methods offered by the class.	Comment only
21 Nov 2011	N-dimensional sparse arrays Creates an N-dimensional sparse array object, for arbitrary N.	Matt J	@Jens: You talked me into it. I've now updated the distribution so that DISPLAY will print only those A(:,:,i,j,k,...) containing non-zero data. For displaying purposes, at least, this should solve your problem. Mimicing the data you described, I'm now able to generate the following 37x37x37x37x37x37x37 data set on a 64-bit platform and get a reasonably instantaneous display: A=ndSparse.sprand(37*ones(1,7),400/37^7) However, I am vaguely concerned that you are pushing the limits of the class by having such a large array volume, even on a 64-bit platform. The class wasn't designed to handle arbitrarily large numel(A), just as ordinary MATLAB 2D sparse matrices were not. I now clarify this a bit more in the description section of the FEX page.	Comment only
18 Nov 2011	N-dimensional sparse arrays Creates an N-dimensional sparse array object, for arbitrary N.	Matt J	@Jens: The reason I don't store my own tables is because then I couldn't piggy back on the fast sparse arithmetic routines of MATLAB's underlying 2D sparse class. I would have to implement my own. In any case, the problem with displaying that you mention is probably not strictly related to data storage. It is related to the fact that the ndSparse DISPLAY method mimics the display method for full arrays and tries to print all "sheets" of the form A(:,:,i,j,k,...) to the screen. Since you have 37^5 sheets, naturally this is going to take some time to disaply to the screen. Upon reflection, I admit that a sparser display would be more appropriate for an ndSparse class. For example, I could modify the DISPLAY method so that it only displays non-zero sheets. On the other hand, as a designer, I can't really anticipate how every end-user would like their data displayed. Would a display of 2D sheets A(:,:,i,j,k,...) offer meaningful information to someone working in 7-dimensional space, like yourself, even if I trimmed it down to the non-zero ones? And would every end-user prefer this? Also, if you only want to display the non-zero data, why not use FIND? Or create your own wrapper for FIND which displays the data the way you want?	Comment only
18 Nov 2011	N-dimensional sparse arrays Creates an N-dimensional sparse array object, for arbitrary N.	Jens Munk Hansen	Hey Matt Nice idea, but bad implementation. I am working with a parameter study and data is extremely sparse, dimensions are 37x37x37x37x37x37x37, but I have less than 400 non-zero elements. The display function takes more than 10 hours to execute. Why not simple store tubles and use an intelligent search?	1
22 Sep 2011	N-dimensional sparse arrays Creates an N-dimensional sparse array object, for arbitrary N.	Alexander	Illustration of my issue with sensitivity: profile on N=1e5; % data points data=rand(N,1); % random data dims=[100,100,100,200000]; ind=NaN(N,4); % random indices ind(:,1)=randi(dims(1),N,1); ind(:,2)=randi(dims(2),N,1); ind(:,3)=randi(dims(3),N,1); ind(:,4)=randi(dims(4),N,1); % (100x100x100) x 200000 A1=ndSparse.build( ind , data, dims); % (100x200000x100) x 100 A2=ndSparse.build( circshift(ind,[0 2]) , data, circshift(dims,[0 2])); size(A1) size(A2) tic; ans1=A1(1,:,:,:); % takes about 0.09 secs toc; ans2=A2(:,:,1,:); % takes about 115 secs !!!! toc; % results are equal w.r.t. dimension shift isequal(ans1,shiftdim(ans2,2)) profile viewer % 99% of time is spent on a line data=builtin('subsref',obj.data,E);	Comment only

Contact us at files@mathworks.com