Definite Sum of density functions

I need to compute :

Sum (from n=1 to N) [dgamma(x,n)*(1-dgamma(k,n))]

Sorry for the form I don't managed to do something esthetic.

Have you got an idea ? I have tried this in vain :

% Try 1
N = 100;
S = 0;
for n = 1:N
  S = S + (dgamma(x,n)*(1-dgamma(k,n)));
end

% Try 2
N = 100;
syms n m
S = symsum(dgamma(x,n)*(1-dgamma(k,n)),n,1,N);

[Michael Haderlein]

Your question is a bit unclear:

What is dgamma (function or array)? If it's an array, will N be the length of dgamma? What is x and k?

[Edwin FOURRIER]

Sorry for this, dgamma is the gamma density function of variables x and k (support) and parameter n.

Answer 1

[Star Strider]

See the documentation on the Gamma Distribution.

[Edwin FOURRIER]

Thank you very much. I had never suspected this problem !

[Star Strider]

My pleasure!