How to use a Digamma function with a complex argument.?

Hello, I'm trying to fit a curve with some experimental values. But I cant solve the equation with complex argument in the Digamma function (psi).

if true
  % code
end
h=6.62606957e-34;
f0=5.45e9;
kB=1.3806488e-23;
%T0=200e-3; %in kelvin
T0=130e-3; 
x=0.5+((h*f0)/(2*pi*1i*kB*T0));
g2=real(psi(sym(x)));
T=200e-3;
x=0.5+((h.*f0)./(2*pi*1i*kB.*T));
g1=real(psi(sym (x)));
delf0=(f-f(7))./f(7);
freq=@(b,x) (b(1)/pi)*(log(x./T0)-(g1-g2));
b0=7.8893e-05;
beta=nlinfit(T,delf0,freq,b0);

---------------- I get the follow error ----------------

if true
  % code
end
Undefined function 'isfinite' for input arguments of
type 'sym'.
Error in nlinfit (line 242)
if funValCheck && ~isfinite(sse), checkFunVals(r); end
Error in f0_temp_fit (line 26)
beta=nlinfit(T,delf0,freq,b0);

What is wrong with the code ? PS: I have not included the data acquisition part in this code above.

Thanks, /C

[Star Strider]

Some problems:

1. Don’t use sym. There is no reason for it in your code;
2. Your ‘g1’ and ‘g2’ are exactly the same, so (g1-g2)=0;
3. ‘T’ has to be a vector the same size as ‘delf0’.