[R] avoid step appearance in plot lines

[Angel Lopez]

How can I improve the aspect of the lines in a line plot?
I want to avoid that between two points the line joining them is breaked 
into "steps".
For example:
plot(1:100,sin(1:100))
lines(1:100,sin(1:100),type='l',lwd=2)
I get that the line joining two points is made up of vertical segments, 
what I basically want is that there are more segments between two points 
so I get the aspect of a true line.
Thanks,
Angel