MATLAB: with My Fixed Point Iteration Program

[pjkily]

Homework Statement

Fixed Point Iteration MATLAB program

Homework Equations

To test for convergence: abs(g'(x))<1

The Attempt at a Solution

Hi all, I am trying to write a Fixed Point Iteration program but when I enter in the command line it kept giving me an error message. Can you please look over my program and tell me what might have gone wrong? Thank you very much!

First, I defined a function in a new M-File:

function y=FUN3(x)
y=5/(sin(x)*exp(-x./2));

Then, I opened up another M-File and wrote the program:

function Xs = FixedIterationRoot3(FUN3,Xest,imax)
syms x FUN3 FunDer3
Xi(1)=Xest;
FUN3=5/(sin(x)*exp(-x./2));
FunDer3 = diff(FUN3) % To find g'(x)

if abs(subs(FunDer3,x,Xest))>=1 % to check if g'(x) diverges
return;
fprintf('not valid')
end

for i=2:imax
Xi(i)=feval(FUN3,Xest);
Xest=Xi(i);
Xs=Xi;
end



When I enter in the command line:
>> xSolutions=FixedIterationRoot3('FUN3',-3,10)

it gave me error message:
syms x FUN3 FunDer3

? Output argument "Xs" (and maybe others) not assigned during call
to
"C:\Users\Jane\Documents\MATLAB\FixedIterationRoot3.m>FixedIterationRoot3".

 

[CEL]

Homework Statement

Fixed Point Iteration MATLAB program

Homework Equations

To test for convergence: abs(g'(x))<1

The Attempt at a Solution

Hi all, I am trying to write a Fixed Point Iteration program but when I enter in the command line it kept giving me an error message. Can you please look over my program and tell me what might have gone wrong? Thank you very much!

First, I defined a function in a new M-File:

function y=FUN3(x)
y=5/(sin(x)*exp(-x./2));

Then, I opened up another M-File and wrote the program:

function Xs = FixedIterationRoot3(FUN3,Xest,imax)
syms x FUN3 FunDer3
Xi(1)=Xest;
FUN3=5/(sin(x)*exp(-x./2));
FunDer3 = diff(FUN3) % To find g'(x)

if abs(subs(FunDer3,x,Xest))>=1 % to check if g'(x) diverges
return;
fprintf('not valid')
end

for i=2:imax
Xi(i)=feval(FUN3,Xest);
Xest=Xi(i);
Xs=Xi;
end



When I enter in the command line:
>> xSolutions=FixedIterationRoot3('FUN3',-3,10)

it gave me error message:
syms x FUN3 FunDer3

? Output argument "Xs" (and maybe others) not assigned during call
to
"C:\Users\Jane\Documents\MATLAB\FixedIterationRoot3.m>FixedIterationRoot3".

In your test for divergence you should attribute a value to Xs before returning.
Also the printf command should come before return, otherwise it will not be executed.