I fear you have a problem with your parentheses. The '>' sign turns to a '+' when the line is incomplete. See the R-FAQ for information. This evaluates but I'm not sure if it's what you want.... fn < -function(x){ (-50*log((sd(x))^2))-50*log(sqrt(2*pi))-(1/2*((mean(x))^2))*(sum((x-(mea n(x))^2))) } fn(1:10) HTH, Andy