[R] barplot or maybe related?

[questions?]

I have two distributions, represented by heights of several intervals.
e.g. the distribution is partitioned into 10 segments, I have
numbers(freq or counts) associated
with each region in the format as:

0.2  0.3
0.1  0.1
.....

0.01 0.02


I want to plot the two distributions side by side in meaning that, for
each region,the
two bars(in barplot) from the two distribution are adjacent to each
other.

If you do barplot(beside=T), the two distribution are plotted side by
side, not interleaved.
I was wondering there are ways to do what I want

Thanks