what is wrong when using fzero

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Vicky
Vicky 2013-2-27
hi!
i would like to compute this:
function z=theta(m)
digits 250;
s=sym('s');
p=0;
q=0;
for i=0:m
p=p+(factorial(2*m-i)*factorial(m)*s^i)/factorial(2*m)*factorial(m-
i)*factorial(i);
q=q+(factorial(2*m-i)*factorial(m)*(-s)^i)/factorial(2*m)*factorial(m-
i)*factorial(i);
end;
r=p/q;
s=taylor(exp(-s)*r-1, s, 150); %taylor expansion
coeff=vpa(sym2poly(sym(s)),250); % c_i
x=sym('x');
sum1=0;
l=1;
for j=(2*m+1):(150+2*m)
sum1=sum1+abs(coeff(l))*x^j;
l=l+1;
end;
bound=vpa((-log(1-sum1))/x,250);
n=fzero(bound,3);
just the last part is important. i think there is something wrong with my use of fzero.. when i want to calculate this, i get this error:
>> theta(2)
??? Error using ==> fzero at 181
If FUN is a MATLAB object, it must have an feval method.
Error in ==> theta at 27
n=fzero(bound,3);

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回答（2 个）

Walter Roberson
Walter Roberson 2013-2-27
You cannot use fzero() on symbolic objects.
If you are going to use symbolic objects, use solve(), or use
feval(symengine, 'numeric::solve', bound, 3)
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Vicky
Vicky 2013-2-28
or if i can use fsolve, where there is an initial point, what i would like. How to form that...

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Carlos
Carlos 2013-2-28
You can use solve instead of fzero

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