[R] question on plot

[Zhongming Yang]

The following commands only draw two lines (blue and red ones) rather
than three lines.
plot(inData[[1]], inData[[2]], type='l', col="blue", );
lines(inData[[1]], mod.data$prepeak, col="green");
lines(inData[[1]], baseline, col="red");

But when I can draw three lines in different diagrams by using 
par(fraw=c(3,1));
plot(inData[[1]], inData[[2]], type='l', col="blue", );
plot(inData[[1]], mod.data$prepeak, type='l', col="green");
plot(inData[[1]], baseline, type='l', col="red");

What's wrong with the first three commands?

Thanks,