[Gnuplot-info] Use of using with matrix

[<she...@be...>]

Hello Gnuploteers

I am using gnuplot to plot some image data as follows

   plot 'k_space.dat' index i matrix with image

the index i chooses which 2D image data set to use in a file containing
multiple 2D image. I would like to be able to label the image with an ID
number (or two) associated with each 2D data set stored in the file. I
have the suspicion I should be able to do this with the "labels"  command
and the
"using" command. The "using" command would specify which bits of data in
the file contain the ID number/s.

My questions are: (1) How should I structure my data file so this can be
done and, (2) How do I use "using" and "label" to do this?

Thanks again!!