Dear All, I am trying to fit some data both as a negative binomial and a zero inflated binomial. For the first case, I have no particular problems, see the small snippet below library(MASS) #a basic R library set.seed(123) #to have reproducible results x4 <- rnegbin(500, mu = 5, theta = 4) #Now fit and check that we get the right parameters fd <- fitdistr(x4, "Negative Binomial") summary(fd) #and mu and theta are as expected #now I add artificially some zeros x5 <- sample(c(x4,rep(0,100))) However, when I artificially add some zeros (case of x5) I am unsure about how to proceed. I found some material online bit.ly/uPVzOT bit.ly/rXnzKi but I wonder if they are an overkill of what I am really after (a fitting a negative binomial with too many zeros). Any suggestion is really appreciated. Many thanks Lorenzo
try: library(pscl) There's a zeroinfl for zero inflated neg. binom. Tyler> Date: Thu, 17 Nov 2011 17:50:46 +0100 > From: lorenzo.isella@gmail.com > To: r-help@stat.math.ethz.ch > Subject: [R] How to Fit Inflated Negative Binomial > > Dear All, > I am trying to fit some data both as a negative binomial and a zero > inflated binomial. > For the first case, I have no particular problems, see the small snippet > below > > library(MASS) #a basic R library > > set.seed(123) #to have reproducible results > > x4 <- rnegbin(500, mu = 5, theta = 4) > > #Now fit and check that we get the right parameters > > fd <- fitdistr(x4, "Negative Binomial") > > summary(fd) > > #and mu and theta are as expected > #now I add artificially some zeros > > x5 <- sample(c(x4,rep(0,100))) > > However, when I artificially add some zeros (case of x5) I am unsure > about how to proceed. > I found some material online > > bit.ly/uPVzOT > bit.ly/rXnzKi > > but I wonder if they are an overkill of what I am really after (a > fitting a negative binomial with too many zeros). > Any suggestion is really appreciated. > Many thanks > > Lorenzo > > ______________________________________________ > R-help@r-project.org mailing list > stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.[[alternative HTML version deleted]]