How to place labels on top of each box in gnuplot?

Question

Hi,

I have an array of data which looks like this [0.5, 0.3, 0.15,0.0, 0.0, -0.09, -0.25,-0.4].

I wanted put a corresponding label (or number) of the boxes on top of the each box to indicate which one is which.

Anybody knows how to do this ??

Thanks.