[pstricks] plot of the sum of the second derivative of a gamma function
Cyrille Piatecki
cyrille.piatecki at univ-orleans.fr
Wed Oct 20 10:43:25 CEST 2010
Dear all,
I ask for a little help I need to plot the second derivative of the
sum of two gamma distribution functions ---
$F_1^{\prime\prime}+F_2^{\prime\prime}$ such that :
\[ F^\prime_1 = \Gamma(x)^{-1}\left[\lambda_1 e^{- \lambda_1 x}
(\lambda_1 x)^(t_1-1)\right]
\]
and
\[ F^\prime_2 = \Gamma(x)^{-1}\left[\lambda_2 e^{- \lambda_2 x}
(\lambda_1 (x-\mu))^(t_2-1)\right]
\]
where incidentaly $\mu$ is the mean of $F_1$ but this is not a problem
since it is easy to know the expectation from a Gamma distribution
from its parameters.
Thanks for the help Cyrille Piatecki
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