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

Question

Shweta Rajoria 2017-9-11

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https://ww2.mathworks.cn/matlabcentral/answers/356067-how-to-calculate-imaginary-part-of-incomplete-gamma-function-in-matlab

编辑： Karan Gill 2017-10-17

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.

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Answer 1

Karan Gill 2017-9-12

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https://ww2.mathworks.cn/matlabcentral/answers/356067-how-to-calculate-imaginary-part-of-incomplete-gamma-function-in-matlab#answer_281231

编辑：Karan Gill 2017-10-17

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

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Shweta Rajoria 2017-9-13

Thank you Karan sir my problem is solved with this.

Karan Gill 2017-9-14

Great! Could you please accept my answer?

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Answer 2

John D'Errico 2017-9-11

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编辑：John D'Errico 2017-9-11

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."

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Shweta Rajoria 2017-9-11

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.

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