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pliszka
Poland
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 Posted - 01/24/2006 : 06:00:24 AM
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| incgamma(a,x)have two parameters x and a, I'd like to know what thehy mean? and what values I should put to obtain for example gamma(x) because in origin there isn't gamma function and I can't use lngamma() |
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Mike Buess
USA
3037 Posts |
Posted - 01/24/2006 : 08:29:15 AM
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If you have Origin 7 or 7.5 you can use Origin C's nag_gamma function. LabTalk's gammaln function works in all versions... gamma(x) = exp(gammaln(x)).
...Here are the expressions for gamma and incgamma found in the programming guide.
gamma(x):
incgamma(a,x):
So incgamma(a,x=infinity) = gamma(a)/gamma(a) = 1, but it's not clear to me how to obtain gamma(a) from incgamma(a,x) for an arbitrary value of x. I suggest you use one of the methods discussed at the top of this post.
Mike Buess
Origin WebRing Member
Edited by - Mike Buess on 01/24/2006 3:18:57 PM |
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sp973
Australia
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larry_lan
China
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Posted - 12/13/2006 : 03:03:25 AM
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Hi Serhiy:
I just compare the OriginC incgamma(x, a) function with Matlab gammainc(x, a) function, the result is the same.
I think you might get the "incorrect result" by using the LabTalk incgamma(a, x) function. Note that the parameters' order is different between LabTalk and OriginC.
Larry
OriginLab Technical Services |
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incgamma()