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Chebfun V4

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Chebfun V4

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30 Apr 2009 (Updated )

Numerical computation with functions instead of numbers.

Editor's Notes:

This file was selected as MATLAB Central Pick of the Week

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Description

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We are pleased to announce the release of Chebfun Version 5, available for download at http://www.chebfun.org/download/

Version 5 has involved a complete rewrite of the code with a focus on clarity to make it more accessible and extensible. The code is hosted on GitHub (https://github.com/chebfun/), and we welcome new developers to get involved.
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Chebfun is a collection of algorithms and an open-source software system in object-oriented MATLAB which extends familiar powerful methods of numerical computation involving numbers to continuous or piecewise-continuous functions. It also implements continuous analogues of linear algebra notions like the QR decomposition and the SVD, and solves ordinary differential equations. The mathematical basis of the system combines tools of Chebyshev expansions, fast Fourier transform, barycentric interpolation, recursive zerofinding, and automatic differentiation.
Here are three quick examples:

What's the integral of sin(sin(x)) from 0 to 10?
>> x = chebfun('x',[0 10]); sum(sin(sin(x)))
ans = 1.629603118459496

What's the maximum of sin(x)+sin(x2) over the same interval?
>> max(sin(x)+sin(x.^2))
ans = 1.985446580874100

What's the solution to u"-xu=1 with zero boundary conditions on [-20,20]?
>> L = chebop(@(x,u)diff(u,2)-x.*u,[-20,20],'dirichlet'); plot(L\1)

For much more extensive list of more in-depth examples, see http://www.chebfun.org/examples/ and http://www.chebfun.org/examples/new/

This release is compatible with MATLAB 7.6 (2008a) and more recent versions.
 
Installation instructions:

1. Unzip the contents of the zip file to a directory. We suggest the name "chebfun" for this directory. Make sure to maintain the existing subdirectory structure of the zip package. (Please note: If you install into the "toolbox" subdirectory of the MATLAB program hierarchy, you will need to click the button "Update toolbox path cache" from the File/Preferences... dialog in MATLAB.)

2. In MATLAB, add the chebfun directory to your path. This can be done by selecting "File/Set Path..." from the main or Command window menus. We recommend that you select the "Save" button on this dialog so that chebfuns are on the path automatically in future MATLAB sessions. (Alternatively, you can put an "addpath" command in your startup.m file, as described in the MATLAB documentation.)

3. A restart of MATLAB may be needed if you want to access the user guides via the Help browser.

4. To check whether the system appears to be working, type "chebtest" at the command window prompt. If a problem is reported, please contact help@chebfun.org with the details (including output of the "ver" command and the file chebtest_report.txt).

5. Point your web browser to the guide/html directory of the Chebfun installation in order to read the user guides.

Please see the file LICENSE.txt for licensing information. For full documentation, guides, and examples, visit http://www.chebfun.org/

Acknowledgements

This file inspired Chebpack, Gauss Quadrature Nodes And Weights., Dynamical System Viewer, and Chebfun.

Required Products MATLAB
MATLAB release MATLAB 7.14 (R2012a)
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Comments and Ratings (19)
21 Nov 2014 Nick Hale

Hi Mehedi

I suggest you download the new version of Chebfun from here:

http://www.mathworks.com/matlabcentral/fileexchange/47023-chebfun

Regards

Nick

17 Nov 2014 Mehedi

Hello,
Great stuff! However, on 'guide - 7' this code segment does not work and gives the following error --

code :
L = chebop(@(x,u) diff(u,2),[0,pi]);
L.bc = 0;
[V,D] = eigs(L);
diag(D)
clf, plot(V(:,1:4))

error:
Error using horzcat
Dimensions of matrices being concatenated are not consistent.

Error in chebop/linearise (line 133)
dom = unique([dom domL domR domO]);

Error in chebop/linop (line 18)
[L bc isLin] = linearise(N,[],linCheck);

Error in chebop/eigs (line 44)
L = linop(N);

I would be happy if you can address this issue with a solution. Thanks in advance.

BR
Mehedi

23 Apr 2013 Nick Hale

Hi Jeff

Sorry for the delay in replying. In your first problem, you haven't quite the boundary condition syntax correct. The following should work:

L = chebop(@(x,u) diff(u,4), [0,1]);
B = chebop(@(x,u) sin(x) + 0*u, [0,1]);
L.lbc = @(u) [diff(u,2), diff(u,3)];
L.rbc = @(u) [diff(u,2), diff(u,3)];

The y''''(x)=lambda*f(x)*y(x) problem should be possible also. Try something like the following, where sin is replaced by the m-file you wish to use to construct f:

f = chebfun(@sin, [0, 1]);
[V, D] = eigs(L, diag(f), 4);

Regards

Nick

P.S. Emailing discuss@chebfun.org or help@chebfun.org should result in speedier replies! :)

08 Apr 2013 Peter Green

Another question: I want to solve the eigenvalues and eigenfunctions of the following equation

y''''(x)=lambda*f(x)*y(x)

Here f(x) is a function defined in a seperate .m file. Is it possible to use chebfun to solve the eigenvalues and eigenfunctions?

Thanks.
Jeff

08 Apr 2013 Peter Green

An excellent software!!! Definitely 5 star.

A quick question. I am using the chebfun function to find the eigenvalues and eigenfunctions of the following boundary value problem

D^4 y=lambda*y, y''(0)=y'''(0)=y''(1)=y'''(1)=0,

where D is the differential operator, lambda is the eigenvalue and the solution y is the corresponding eigenfunction.

I used the following code in chebfun:

L = chebop(@(x,u) diff(u,4), [0,1]);
L.lbc = @(u) diff(u,2);
L.lbc =@(u) diff(u,3);
L.rbc = @(u) diff(u,2);
L.rbc =@(u) diff(u,3);
[V,D] = eigs(L,trunc);
disp(diag(D)), toc

HOWEVER, the below error was reported

Error using eig
Matrix must be square.

Error in linop/eigs>bc_eig (line 288)
[V,D] = eig(full(Amat),full(Pmat));

Error in linop/eigs (line 94)
[V1,D1] = bc_eig(A,B,33,33,0,map,breaks);

Error in chebop/eigs (line 57)
[varargout{1:nargout}] = eigs(L,varargin{:});

Looks like I am on the right track but some nonsquare matrix caused that error. Sincerely appreciate your comments and suggestions.

Thanks.
Jeff

15 Feb 2013 Raghuram  
23 Oct 2012 Shashank

Perfect toolbox for somebody doing numerical analysis for the first time!

16 Nov 2011 Mark Shore

There is just so much to learn from this topnotch collection of powerful routines.

16 Nov 2011 Mark Shore

There is just so much to learn from this topnotch collection of powerful routines.

16 Nov 2011 Mark Shore  
27 Oct 2011 Chebfun Team

Hi Jiro,

Thanks! We're currently in the process of moving to the new OOP system in our development release, which you can find on our website: http://www.maths.ox.ac.uk/chebfun/

27 Oct 2011 Jiro Doke

I really like the comprehensive User's Guide that you include with this package.

Do you have a plan to implement this using the new MATLAB Class system?

29 Jun 2009 Erdal Bizkevelci  
11 Jun 2009 Siyi Deng

this toolbox is awesome.

25 May 2009 Erdal Bizkevelci  
07 May 2009 John D'Errico

Thanks Tobin - that was what i was looking for. Those files are very readable, clearly explaining what a chebfun is and how to use them. I'll now call this a complete package.

I've had the time to do a little more perusal of these tools now too. They work on my Mac, which is sometimes an issue.

07 May 2009 Toby Driscoll

The guide directory included in the package has 8 published scripts that contain dozens of examples in tutorial style. The resulting HTML files are also installed in the Help Browser under the "Chebfun Toolbox" heading.

04 May 2009 John D'Errico

I've not tried this out, nor tested it yet. That will take some time. But what I've seen suggests this will be interesting and potentially useful. A lot of effort has been invested here in these tools.

The only thing I'd have liked to see is a published set of demos, with more explanation around how to use it and what the demos are showing. There is a directory (chebtests) of some tests of the tools, but they have virtually no comments in them. Derek has a good suggestion, to read the paper by Trefethen. Here are a few links of interest:

http://www.comlab.ox.ac.uk/nick.trefethen/trefethen_functions.pdf

http://www.comlab.ox.ac.uk/nick.trefethen/ppt_revised.pdf

http://www.comlab.ox.ac.uk/chebfun/publications/driscoll_born_tref.pdf

The papers shown are quite readable. I'd highly recommend them.

My only source of dissatisfaction here is with a lack of examples. These files need extensive demos and DOCUMENTED examples that explain how to use them for the person who might be interested in using them. The fact is, it does not look like that would be difficult to do, and I'd welcome that addition.

My gut says these tools are worth a 5 star rating, IF you know how to use them and what they do. Without a good set of clearly documented examples, my gut wants to rate them as only 4 stars.

02 May 2009 Derek O'Connor

An excellent system. Passed all tests with Matlab R2008a 64 bit with Windows Vista 64.

Read Trefethen's paper "Computing Numerically with Functions Instead of Numbers" which is a nice short introduction to Chebfun.

http://www.comlab.ox.ac.uk/nick.trefethen/home.html

Derek O'Connor

Updates
30 Apr 2009

Changed the screenshot of the logo.

10 Jun 2009

New chebfun release v. 2.0501. Release notes can be found at http://web.comlab.ox.ac.uk/projects/chebfun/notes_V2_0501.html

12 Jun 2009

Summary corrected.

21 Jun 2009

Updated license information

08 Jan 2010

Added version number to title and some minor changes to the description.

25 Oct 2011

Updated information on new release.

16 Nov 2011

Updated to most recent software release (V4.1).

16 Nov 2011

The .zip file didn't seem to have been updated in the previous resubmission.

05 Apr 2012

Updated to v4.2.2194.

Release notes at www.chebfun.org/notes/

20 Jun 2014

Rename this as V4. V5 will be released on FileExchange (via GitHub) very soon.

20 Jun 2014

Removing V5 notification. Didn't expect the change to happen instantly..

24 Jun 2014

Announce V5 release.

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