[R] Description of x-axis

[Christian Oswald]

Hello,

I have made a barplot with some data and need a description below the
x-axis. For example there are 20 values and I need a description "2003"
for the first four values, then "2005" for the next eleven and "2006"
for the last five values.

I want the description below the x-axis-labels and above the x-axis title.

Thanks,

Christian