Plotting argument of complex function with syms parameter

>> ezplot(atan(imag((3*exp(pi*l*4*i) + 1)/(9*exp(pi*l*4*i) - 1)), real((3*exp(pi*l*4*i) + 1)/(9*exp(pi*l*4*i) - 1)))) Error using inlineeval (line 15) Error in inline expression ==> arg(imag((3.*exp(pi.*l.*(4.*i)) + 1)./(9.*exp(pi.*l.*(4.*i)) - 1)).*i + real((3.*exp(pi.*l.*(4.*i)) + 1)./(9.*exp(pi.*l.*(4.*i)) - 1))) Undefined function 'arg' for input arguments of type 'double'.

Error in inline/feval (line 34) INLINE_OUT_ = inlineeval(INLINE_INPUTS_, INLINE_OBJ_.inputExpr, INLINE_OBJ_.expr);

Error in ezplotfeval (line 52) z = feval(f,x(1));

Error in ezplot>ezplot1 (line 469) [y, f, loopflag] = ezplotfeval(f, x);

Error in ezplot (line 145) [hp, cax] = ezplot1(cax, f{1}, vars, labels, args{:});

Error in sym/ezplot (line 61) h = ezplot(fhandle(f));

Is there another way of plotting the function?

[Walter Roberson]

There are no syms parameters in your expression.

Answer 1

[Walter Roberson]

arg(C) with C a complex number, is atan2(imag(C), real(C))

[Bruno]

ezplot(atan2(imag((3*exp(pi*l*4*i) + 1)/(9*exp(pi*l*4*i) - 1)), real((3*exp(pi*l*4*i) + 1)/(9*exp(pi*l*4*i) - 1))),[0,1])

Undefined function 'atan2' for input arguments of type 'sym'.

I have also used atan instead. I manage to define the function bu not plot it.

The syms parameter is in the expression: it's l (see argument of exp).

Bruno

[Walter Roberson]

Which is the symbolic variable there?

Anyhow: see http://www.mathworks.co.uk/matlabcentral/answers/65848-abs-and-angle-of-complex-number-with-symbolic-object