fsolve and complex solution?

2012 6 18
1 个回答
回答已采纳
6 次查看（30 天）

0 个投票

Hello,
my test function is f=x^2+1 the slution is easy : x1=i orx2=-i (both are imaginary)
fsolve is not finding these values...why? fsolve returns 0 for a solution??
Thank you.

4 个评论
显示 2更早的评论 隐藏 2更早的评论

Walter Roberson
Walter Roberson 2012-6-18
Please show your test code?
John Miller
John Miller 2012-6-18
x0 = 0; % Make a starting guess at the solution
options=optimset('Display','iter'); % Option to display output
[x,fval] = fsolve(@myfun,x0,options) % Call solver
with the funciotn:
function F = myfun(x)
F = x^2+1;
end
Walter Roberson
Walter Roberson 2012-6-18
And you are not getting any warning message about it not being able to solve the problem?
I take it you overlooked this line in the documentation:
"fsolve only handles real variables. When x has complex variables, the variables must be split into real and imaginary parts."
John Miller
John Miller 2012-6-18
fsolve returns the following message:
No solution found.
fsolve stopped because the problem appears regular as measured by the gradient,
but the vector of function values is not near zero as measured by the
default value of the function tolerance.
<stopping criteria details>
x =0
fval =1
I should split x in real and imaginary? Like this:
F = (r+i*s)^2+1; ?

请先登录，再进行评论。

请先登录，再回答此问题。

 采纳的回答

Walter Roberson
Walter Roberson 2012-6-18

0 个投票

function F = myfun(ripair)
x = ripair(1) + ripair(2)*1i;
F = x^2+1;
if imag(F) ~= 0; F = 10^5; end %you need to emit finite real value from myfun
end
and make sure your x0 has a pair of values.

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 Linear Algebra 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by