Converting function file to Anonomys function.

Question

Tom Craven 2015-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/221837-converting-function-file-to-anonomys-function

评论： Stephen23 2015-6-2

Given we have the function file

function y = lorenz(t,x,sigma,rho,beta)
% INPUT: t is a a real value indicating time
% x is a column vector of size 3 x 1
% sigma, rho, beta are parameters of the Lorenz
% equations
% OUTPUT: y is a column vector of size 3 x 1 that gives
% the right hand side of the Lorenz equations
y=[0;0;0];
x=x+t;
y(1)=sigma*(x(2)-x(1));
y(2)=x(1)*(rho-x(2))-x(3);
y(3)=x(1)*x(2)-beta*x(3);
end

How can we convert this into a Anonymous function

f = @(t,x) lorenz(t,x,sigma,rho,beta)

??.

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Tom Craven 2015-6-2

编辑：Walter Roberson 2015-6-2

在 MATLAB Online 中打开

%This is my main.m function. 
% main.m, Script to test all of the functions 
%PART 1. 
%Set the values, rho, sigma and beta. 
rho=28; 
sigma = 10; 
beta=  8/3;
%Part 2
%Define the right hand side of the Lorentz system (1)
%as an anonymous function. 
f = @(t,x) lorenz(t,x,sigma,rho,beta);
%f = @(t,x) lorenz(t,x,sigma,rho,beta);
%PART 3
%Define a vector of equally spaced grid points 
k=1; 
h=10^(-k); 
tfinal=1; 
t=[0:h:tfinal]; 
%PART4 
%Set the initial data points for y0. 
y0=[-1;3;4]; 
%PART 5 
%Ask the user which method is to be used to 
%Solve the system. 
prompt='Please enter method you wish to use to solve system'
disp('Eulers Method (EM)');
disp('Runge-Kutta order 4 (RK4)');
disp('Implicit Runge-Kutta Method (IRK4)'); 
method=input(prompt,'s'); 
%PART 5 
%Solve the systmem using the method which the user
%has chosen. Store the results in a matrix Y of size
%3*N, where N is the length of the vector t.
switch method
      case 'EM'
         disp('Euler Method'); 
         y= EulerSolver(f,t,y0);
      case{ 'RK4'} 
        printf('Runge-Kutta Method\n');
      case{ 'IRK4'}
        printf('Implicit Runge Kutta method'); 
      otherwise
         disp('Wrong input format'); 
end

Walter Roberson 2015-6-2

Please show the complete trace of the "too many input arguments" error.

Stephen23 2015-6-2

If you are getting an error message please give us the complete message (i.e. all of the red text). We need this to know what is happening.

Also please do not insert empty lines into your code, it makes it difficult to read on this forum.

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Answer 1

Guillaume 2015-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/221837-converting-function-file-to-anonomys-function#answer_181172

在 MATLAB Online 中打开

If you're asking how to replace the whole code in your lorenz function by an anonymous function, I'm not sure it's a good idea as it's not going to be very readable due to the severe limitations of anonymous functions in matlab.

This would be something like:

f = @(t, x) [sigma*(t+(x(2)-x(1))), (x(1)+t)*(rho-x(2)-t)-x(3)-t, (x(1)+t)*(x(2)+t)-beta*(x(3)+t)];

Keep your function in a file. It's a lot clearer.

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Sean de Wolski 2015-6-2

编辑：Sean de Wolski 2015-6-2

^This

And not just clearer; faster also!

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Answer 2

Nobel Mondal 2015-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/221837-converting-function-file-to-anonomys-function#answer_181167

编辑：Nobel Mondal 2015-6-1

在 MATLAB Online 中打开

fH = str2func('lorenz');
y = feval(fH,t,x,sigma,rho,beta);

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Tom Craven 2015-6-1

Is the second line supposed to read f= feval(fH,t,x,sigma,rho,beta);

?

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Converting function file to Anonomys function.

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