mydf <- data.frame(V1=c(2,NA,NA,NA,6),V2=c(4,5,NA,7,6),V3=c(3,4,NA,3,9))
plot(NA,xlim=c(0,nrow(mydf)+1),ylim=c(min(mydf,na.rm=TRUE)-1,max(mydf,na.rm=TRUE)+1))
mapply(function(x,color){
dat <- na.omit(cbind(1:length(x),x))
lines(dat[,1],dat[,2],col=color)
},mydf,c("red","blue","green"))
