i am trying to find omega using while

I need to determine omega.

I came so far to think that i need a while loop to do so but I get an error, so want to check my syntax is correct.

%Exercise 3

m=[3.3e2 3.3719e2 2.7564e2 2.2902e2 1.9140e2 1.6692e2 1.5947e2...
    8.4519e1 4.7877e1 3.3029e1 2.5357e1 1.9990e1]; %constants given

py_guess=zeros(1,length(x));
pz_guess=zeros(1,length(x));

py_guess(2:length(x))=100;
pz_guess(2:length(x))=100;

tolerance=0.001;

while
omega=sqrt(pz_guess(12)/(u_zGuess(12)*m(12)))
if
    omega_old=omega
    break 
else
    [u_yGuess,u_zGuess]=UyUzCalcGuess(x,py_guess,pz_guess,EI1,EI2,B);
end
end

my function runs as it should.

Assignment3
Error: File: Assignment3.m Line: 210 Column:
6
Expression or statement is incomplete or
incorrect.

Answer 1

[Walter Roberson]

The syntax for while is

while CONDITION
   ...
end

If you want your loop to run until you break, then use

while true
   ...
end

[Casper Stroem]

i understand what you wrote but i am unsure of my syntax.

I have:

omega=0;
omega_old=0;

while omega_old<omega
[u_yGuess,u_zGuess]=UyUzCalcGuess(x,py_guess,pz_guess,EI1,EI2,B)
    omega=sqrt((pz_guess(12)/(u_zGuess(12)*m(12))));
    omega=omega_old
  pz_guess=omega^2*m*(u_zGuess/(sqrt((u_zGuess(12)^2)+(u_yGuess(12)^2))));
  Py_guess=omega^2*m*(u_yGuess/(sqrt((u_zGuess(12)^2)+(u_yGuess(12)^2))));
end

what i am trying to achieve is to get omega to converge with the formulas in my loop. but when i run it it just gives omega=0

[Walter Roberson]

You start omega and omega_old at the same value. 0<0 is false, so your body of your while will never be executed. You should initialize omega_old to -infinity

Caution: your code calculates a new value for omega and then promptly assigns omega_old to omega instead, and your code never changes omega_old

[Casper Stroem]

omega_old=0;
omega=0;

while omega_old<=omega || omega_old==0 || omega==0

      [u_yGuess,u_zGuess]=UyUzCalcGuess(x,py_guess,pz_guess,EI1,EI2,B)

      omega_old=sqrt((pz_guess(12)/(u_zGuess(12)*m(12))));

      pz_guess=omega^2*m.*(u_zGuess/(sqrt((u_zGuess(12)^2)+(u_yGuess(12)^2))));

      Py_guess=omega^2*m.*(u_yGuess/(sqrt((u_zGuess(12)^2)+(u_yGuess(12)^2))));

      omega_old=omega
  end

This is what i have so far but it is stuck in an inifite loop.

I need help how to resolve this and find the frequency omega.

[Walter Roberson]

You have

        omega_old=sqrt((pz_guess(12)/(u_zGuess(12)*m(12))));

which assigns to omega_old. Then you have

        omega_old=omega

which assigns a different value to omega_old . Meanwhile, you have not assigned a value to omega .

omega_old = -inf;
omega = 0;
while omega_old <= omega
  omega_old = omega;
  omega = ....
end

[Casper Stroem]

thank you! it is running now and i am getting values, however it is not converging before i get an error with matrix exceeds index