Hi, The solution x to the equation is the parmater lambda = x/2 of a Poisson distribution with probability of 0.05 for the number of occurrence 2 or fewer. -- View this message in context: http://r.789695.n4.nabble.com/How-to-solve-this-complex-equation-tp4702997p4703070.html Sent from the R help mailing list archive at Nabble.com.