[R] problem with an IF statement?

[tom wright]

Can somebody please take a look at this and tell me whats going wrong?
It seems to be parsing wronly around the 'if' statement and gives me a
directory listing.
Thanks in advance
Tom
N.B. datan is an invented dataset


xvals<-c(1,0.4,0.2)
datan<-data.frame(s1=c(3,4,5),s2=c(5,5,5),s3=c(21,55,34),s4=c(5,3,2))

datan$sint<-NA
datan$sgrad<-NA
for(icount in 1:dim(datan)[1]) {
	yvals<-c(datan[icount,4],datan[icount,3],datan[icount,2])
	if((is.na(yvals[1]) + is.na(yvals[2]) + is.na(yvals[3]))<2) {
		g<-lm(yvals~xvals)
		datan$sint[icount]<-g$coef[1]
		datan$sgrad[icount]<-g$coef[2]
	}
}