Hi everyone!! I have new probability mass function which has the following form( kindly see the image please) http://r.789695.n4.nabble.com/file/n4635047/abc.jpg Here alpha and beta are two parameters and I need to estimate those parameters using Maximum Likelihood Estimation Method( mle2 available in bbmle package) . In thet function I need to define the log-likelihood of the above pmf. Please advice me how I can define a function which has a sum which runs from zero to infinity in R? Thank you . -- View this message in context: http://r.789695.n4.nabble.com/Defining-a-pmf-which-has-sum-from-zero-to-infinity-tp4635047.html Sent from the R help mailing list archive at Nabble.com.