I replicated your error. tau2ca <- NA if (tau2ca==0) {x <- 0.01} else {x <- tau2ca} Hope it helps. And I couldn't replicate your second program, but it seems ok. ----- A R learner. -- View this message in context: http://r.789695.n4.nabble.com/conditonal-if-tp2308568p2308578.html Sent from the R help mailing list archive at Nabble.com.