library(plm, pglm)

data("PatentsRDUS", package="pglm”)

Poisson <- pglm(patents ~   log(rd)  + as.numeric(year)+ center(log(capital72)*as.numeric(year)) , PatentsRDUS,
           family = poisson(link=log), model = "within", index = c("cusip", "year"))

LogLin <- plm( log(patents+ 0.001) ~   log(rd)+ as.numeric(year)+center(log(capital72)*as.numeric(year)) , PatentsRDUS,
                model = "within", index = c("cusip", "year"))

summary(Poisson)

summary(LogLin)