Undefined function 'power' for input arguments of type 'function_handle'. for some Implicit function

I'm trying to plot a "little bit" complicated Implicit function:

for g=1.5 and f=1;

my code was:

g=1.5; %GN
f=1; %epsilon_1
Fun=@(x,y) sqrt((x.^2-y.^2+g^2-f^2)^2+4*x.*y)+g^2+(g*sqrt(2*(x.^2-y.^2+g^2-f^2+sqrt((x.^2-y.^2+g^2-f^2)^2+4*x.*y))))/(tanh((sqrt(2*(x.^2-y.^2+g^2-f^2+sqrt((x.^2-y.^2+g^2-f^2)^2+4*x.*y)))/(g))))
fimplicit(Fun)

but I got the Error code:

Undefined function 'power' for input arguments of type 'function_handle'.

Can anyone please help me to understand what to do in this case?

[Cris LaPierre]

What version of MATLAB are you using?

[Daniel Vainshtein]

R2020b

[Cris LaPierre]

You are missing some closing parenthese in the fraction portion of your equation (one in the numerator, 2 in the denominator). Can you please correct?

[Daniel Vainshtein]

In the Lyx section or in the matlab code?

[Daniel Vainshtein]

Fun = @(x,y) sqrt((x.^2-y.^2+g^2-f^2)^2+4*x.*y)+g^2+(g*sqrt(2*(x.^2-y.^2+g^2-f^2+sqrt((x.^2-y.^2+g^2-f^2)^2+4*x.*y))))/(tanh((1/g)*(sqrt(2*(x.^2-y.^2+g^2-f^2+sqrt((x.^2-y.^2+g^2-f^2)^2+4*x.*y))))))

Answer 1

[Cris LaPierre]

I'm not able to recreate the same error message. It would appear the code you have shared here does not match the code you are running that is creating the error. Specifically, no function handle is being raised to a power in your example.

I do get a warning with your example about array inputs. To fix this, use elementwise operators where appropriate

Fun=@(x,y) sqrt((x.^2-y.^2+g^2-f^2).^2+4*x.*y)+g^2+(g*sqrt(2*(x.^2-y.^2+g^2-f^2+sqrt((x.^2-y.^2+g^2-f^2).^2+4*x.*y))))./(tanh((sqrt(2*(x.^2-y.^2+g^2-f^2+sqrt((x.^2-y.^2+g^2-f^2).^2+4*x.*y)))/(g))));
%                                  ^^                                                                   ^^            ^^                                                         ^^                         

I can recreate your error message if I break the equation into smaller equations, and combine them to form the bigger equation. Here, the fix is to include the (x,y) inputs when using the handle.

% Works
g=1.5; %GN
f=1; %epsilon_1
eq1 = @(x,y) x.^2-y.^2+g^2-f^2;
eq2 = @(x,y) sqrt(eq1(x,y).^2+4*x.*y);
Fun = @(x,y) eq2(x,y) + g^2 + g*sqrt(2*(eq2(x,y) + eq1(x,y)))./(tanh(sqrt(2*(eq2(x,y) + eq1(x,y)))/g));
fimplicit(Fun)

% Causes error
eq2 = @(x,y) sqrt(eq1.^2+4*x.*y);
%                    ^ removed the (x,y) inputs. Now code is trying to square a function handle, resulting in an error.
Fun = @(x,y) eq2(x,y) + g^2 + g*sqrt(2*(eq2(x,y) + eq1(x,y)))./(tanh(sqrt(2*(eq2(x,y) + eq1(x,y)))/g));
fimplicit(Fun)

Warning: Error updating ImplicitFunctionLine.

Undefined function 'power' for input arguments of type 'function_handle'.