[R] Axis label spanning multiple plots

[Andre Nathan]

Hello

I need to plot 3 graphs in a single column; the top two plots have the
same title, and I would like it to be written only once, centered
horizontally and spanning the two plots. Something like


  t +------------+
    |            |
  i |            |
    |            |
  t +------------+
  
  l +------------+
    |            |
  e |            |
    |            |
  1 +------------+

  t +------------+
  i |            |
  t |            |
  l |            |
  e |            |
  2 +------------+

       x-title

Is there a parameter which allows me to do that automatically, or should
I use text() and position the title manually?

Thanks in advance,
Andre