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zayed
zayed 2011-11-29
Hi, I have the following code but when i run it gives an error . The code :
function lambda = drive_zr17t9001
format short e;
Params = load('saved_data.mat');
theta = pi/2;
zeta = cos(theta);
I = eye(Params.n,Params.n);
Q = zeta*I-Params.p*Params.p';
%T is a matrix(5,5)
Mroot = Params.M.^(1/2); %optimization
T = Mroot*Q*Mroot;
%find the eigen values
E =real( eig(T));
%find the negative eigen values -- %find the smallest negative eigen value
gamma = min(E);
%now solve for lambda
bounds = sort([0, -1/gamma]); %in case gamma is positive
M_inv = inv(Params.M); %optimization
lambda = fzero(@(lambda) zr17t9001(lambda,M_inv,Q,Params.zm),bounds); %do the searching
% end
function r = zr17t9001(lambda, M_inv, Q, zm)
Winv = inv(M_inv+lambda.*Q);
r = -(Params.zm)'*M_inv*Winv*Q*Winv*M_inv*(Params.zm);
%end
The error
??? Error using ==> fzero
FZERO cannot continue because user supplied function_handle ==> @(lambda) zr17t9001(lambda, M_inv, Q, Params.zm)
failed with the error below.
Undefined variable "Params" or class "Params.zm".
Error in ==> drive_zr17t9001 at 19
lambda = fzero(@(lambda) zr17t9001(lambda, M_inv, Q, Params.zm), bounds); %do the searching

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采纳的回答

Walter Roberson
Walter Roberson 2011-11-29
[Edited to define the anonymous function as a separate step]
function lambda = drive_zr17t9001
format short e;
Params = load('saved_data.mat');
theta = pi/2;
zeta = cos(theta);
I = eye(Params.n,Params.n);
Q = zeta*I-Params.p*Params.p';
%T is a matrix(5,5)
Mroot = Params.M.^(1/2); %optimization
T = Mroot*Q*Mroot;
%find the eigen values
E =real( eig(T));
%find the negative eigen values -- %find the smallest negative eigen value
gamma = min(E);
%now solve for lambda
bounds = sort([0, -1/gamma]); %in case gamma is positive
M_inv = inv(Params.M); %optimization
zm = Params.zm;
Lz = @(lambda) zr17t9001(lambda,M_inv,Q,zm);
lambda = fzero(Lz,bounds); %do the searching
% end
function r = zr17t9001(lambda, M_inv, Q, zm)
Winv = inv(M_inv+lambda.*Q);
r = -zm'*M_inv*Winv*Q*Winv*M_inv*zm;
%end
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zayed
zayed 2011-11-30
Can you help in Newton Raphson methods in matlab for the function and the same data in the previous code,please .
Walter Roberson
Walter Roberson 2011-11-30
Sorry, I have other things to do. You can find plenty of Newton Raphson implementations around, as the technique is a common course assignment.

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更多回答（1 个）

Matt Tearle
Matt Tearle 2011-11-29
Change the instances of Params.zm in your subfunction zr17t9001 to just zm. (Leave them as they are in the main function drive_...)
Here's why: in the subfunction, you define zm as an input. You are not passing the whole Params structure in, just one particular value that, locally, is called zm.
Note: I copied exactly what you pasted, made the change I suggested (change r = -(Params.zm)'*M_inv*Winv*Q*Winv*M_inv*(Params.zm); to r = -(zm)'*M_inv*Winv*Q*Winv*M_inv*(zm);) and it worked fine for me. Obviously I had to create a saved_data.mat with some fake data in it.
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zayed
zayed 2011-11-30
It gives "Not enough input arguments".
Matt Tearle
Matt Tearle 2011-12-1
What gives this error? Where is this error coming from? As a variation on Walter's suggestion, put these three lines *before* the call to fzero (and, ideally, comment out the fzero line).
l = linspace(0,-1/gamma);
z = arrayfun(Lz,l);
plot(l,z)
Do you get a plot? If so, does it look like something you were hoping for? In particular, does it have any zeros? You could also dive in and look at the values you're getting for z to see if your function is doing what you expect it to do.

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