What am I doing wrong? (Trying to construct a while loop)

V0=10

h_bar_SQ=0.076

E=0:0.1:10

a=0.3

Mass=1

alpha=sqrt(2.*Mass.*E/h_bar_SQ);

beta=sqrt(2.*Mass.*(V0-E)/h_bar_SQ);

F_even=beta.*cos(alpha.*a)-alpha.*sin(alpha.*a)

E=fzero(F_even)

while 
    E=fzero(F_even);
    if
        E=Nan; 
        break
    else 
        a=a-0.010;
    end
end

>> scriptmatlab Error: File: scriptmatlab.m Line: 10 Column: 7 Expression or statement is incomplete or incorrect.

>> scriptmatlab Error: File: scriptmatlab.m Line: 12 Column: 7 Expression or statement is incomplete or incorrect.

Line 10 is where is says while and line 12 is where it says if

[Richard]

I guess I need to add something beside while and if? What?

Answer 1

[Wayne King]

One thing is your missing an "end"

if true
  % code
endV0=10
h_bar_SQ=0.076
E=0:0.1:10
a=0.3
Mass=1
alpha=sqrt(2.*Mass.*E/h_bar_SQ);
beta=sqrt(2.*Mass.*(V0-E)/h_bar_SQ);
F_even=beta.*cos(alpha.*a)-alpha.*sin(alpha.*a) 
E=fzero(F_even)

while 
    E=fzero(F_even);
    if
        E=Nan; 
        break
    else 
        a=a-0.010;
    end
end 
end

You were missing an "end" for your initial if statement. The other thing is what kind of while statement are you trying to construct here? fzero() returns a value. What condition are you trying to test?

How about something like

while ~isnan(fzero( ))

[Richard]

"Investigate the dependence of the lowest two eigenvalues of the square well upon V0 (with fixed a=0.3 /) and a(with fixed V0= 10), and plot your results. What is the smallest well width that will support two bound states?"

Thats the question to the assignment. Im trying to find the lowest value of a which has units of length for which two bound states(Energies) can be supported.

Energy would be the variable E.

Answer 2

[Walter Roberson]

Your syntax

    if
        E=Nan; 
        break
    else 
        a=a-0.010;
    end

is not valid. "if" needs to be followed by a condition, and E=Nan; is not a condition.

Answer 3

[Richard]

Can someone then rewrite it in the correct format?

[Walter Roberson]

Please use "Comment on this Answer" instead of creating new Answers.

while true
  do a computation
  if result of computation has some property
    break
  end
  change something about one or more of the variables involved in the computation
end