How to calculate imaginary part of incomplete gamma function in matlab.

I am calculating the coverage probability of massive MIMO systems. During which i need to calculate imaginary part of incomplete gamma function. But i run code shown below error is:Undefined function 'gammanic' for input arguments of type 'double'.

Error in i_gamma (line 3) y= exp(gammanic(2/a, 2*1i));

Code is as follows

syms  y z 
a=4;
y= exp(gammanic(2/a, 2*1i));
z =imag(y)

Thanks in advance.

Answer 1

[Karan Gill]

You can find "gammainc" for imaginary input values using the Symbolic "igamma" function. Carefully read the note in the "Description" on how to do this: https://www.mathworks.com/help/symbolic/igamma.html

[Shweta Rajoria]

Thank you Karan sir my problem is solved with this.

[Karan Gill]

Great! Could you please accept my answer?

Answer 2

[John D'Errico]

I might point out that gammainc is the name of the incomplete gamma function. Not gammanic. Misspelling a function name tends to work poorly.

Regardless, It looks like gammainc does not accepts complex arguments. As well, the symbolic toolbox does not have an incomplete gamma.

Finally, you state that you need to compute the imaginary part of the GAMMA function. You did not say you need the INCOMPLETE gamma function. So if you really need gamma, why are you apparently trying to use gammainc?

To quote you: "How to calculate imaginary part of gamma function in matlab."

[Shweta Rajoria]

Thanks for the answer sir. I want to calculate it for gammainc by mistake i have written gamma. If you have any idea then please explain. Thanks in advance.