convolution of the double exponential distribution
On 12/22/2005 7:56 PM, Bickel, David wrote:
Is there any R function that computes the convolution of the double exponential distribution? If not, is there a good way to integrate ((q+x)^n)*exp(-2x) over x from 0 to Inf for any value of q and for any positive integer n? I need to perform the integration within a function with q and n as arguments. The function integrate() is giving me this message: "evaluation of function gave a result of wrong length"
Under the substitution of y = q+x, that looks like a gamma integral. The x = 0 to Inf range translates into y = q to Inf, so you'll need an incomplete gamma function, such as pgamma. Be careful to get the constant multiplier right. Duncan Murdoch