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21 Oct 2014 Screenshot Chebfun Chebfun is an open-source package for numerical computation with functions to 15-digit accuracy Author: Chebfun Team approximation, interpolation, quadrature, integration, numerical analysis, ode 69 0
  • 5.0
5.0 | 2 ratings
24 Jun 2014 Screenshot Chebfun V4 Numerical computation with functions instead of numbers. Author: Chebfun Team numerical analysis, interpolation, approximation, spectral methods, differential equation..., chebfun 168 13
  • 5.0
5.0 | 11 ratings
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27 Oct 2011 Chebfun V4 Numerical computation with functions instead of numbers. Author: 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/

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25 Jun 2014 Chebfun Chebfun is an open-source package for numerical computation with functions to 15-digit accuracy Author: Chebfun Team Ehsan

21 Jun 2014 Chebfun Chebfun is an open-source package for numerical computation with functions to 15-digit accuracy Author: Chebfun Team Alex

23 Apr 2013 Chebfun V4 Numerical computation with functions instead of numbers. Author: Chebfun Team Hale, Nick

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 Chebfun V4 Numerical computation with functions instead of numbers. Author: Chebfun Team Green, Peter

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 Chebfun V4 Numerical computation with functions instead of numbers. Author: Chebfun Team Green, Peter

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

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