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

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Richard
Richard 2013-11-14
评论： Walter Roberson 2013-11-14
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

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回答（3 个）

Wayne King
Wayne King 2013-11-14
编辑：Wayne King 2013-11-14
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( ))
  1 个评论
Richard
Richard 2013-11-14
编辑：Richard 2013-11-14
"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.

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Walter Roberson
Walter Roberson 2013-11-14
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.
Richard
Richard 2013-11-14
Can someone then rewrite it in the correct format?
  1 个评论
Walter Roberson
Walter Roberson 2013-11-14
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

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