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### Incomplete gamma function With real but negative x

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```Hi,

I need help with the incomplete gamma function with real but negative
fraction value of x. I found the M_Igamma(x,a)in Meron
Library(http://www.astro.washington.edu/deutsch/idl/htmlhelp/slibrary23.html)
which works for both real and complex  x. However, I notice that
M_Igamma (x,a),  for a real but negative fraction value of x, give
only the real part. If any body knows how to deal with this problem

Dag
```
 0

```In article <162586e3.0310130746.5997d5bf@posting.google.com>, biomedthesis2002@yahoo.com (New2IDL) writes:
>Hi,
>
> I need help with the incomplete gamma function with real but negative
>fraction value of x. I found the M_Igamma(x,a)in Meron
>Library(http://www.astro.washington.edu/deutsch/idl/htmlhelp/slibrary23.html)
>which works for both real and complex  x. However, I notice that
>M_Igamma (x,a),  for a real but negative fraction value of x, give
>only the real part. If any body knows how to deal with this problem

Well, I can actually help you on this one.  First, though, I suggest
you use the updated version of the routine (called Igamma_mm), you can
find it in my library on the RSI users contribution page.

Now, as for your question, Igamma_mm returns an output which is of the
same numerical type as x (no lower than float, though).  So, if x is real,
so will be the output.  If you want a full complex output, you need
complex input.  See below:

IDL> print, igamma_mm(-0.069,2.2)
0.000976233
IDL> print, igamma_mm(complex(-0.069),2.2)
(  0.000976233,  0.000709275)

Hope this helps.

Mati Meron                      | "When you argue with a fool,
meron@cars.uchicago.edu         |  chances are he is doing just the same"
```
 0
Reply mmeron (89) 10/13/2003 7:48:55 PM

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