[Gnuplot-info] request for help plotting surface (pm3d) with data file -- no data are being plotted

[D. R. E. <doc...@gm...>]

Using gnuplot 4.0, patch level 0.

I apologise for this elementary question, but I have spent more than
an hour trying to do something very simple, with no success (and also
spent time additional googling for an example, to no avail).

I have a data file in a simple x y z format. It starts like this:

1 0 0
1 10 0
1 20 0
1 30 0
1 40 0
1 50 0
1 60 0
1 70 0
1 80 0

and ends like this

249 24950 0
249 24960 0
249 24970 1
249 24980 0
249 24990 1

It contains a total of ~350,000 lines.

If I start gnuplot and simply run "splot <filename>" I get a plot, so
the file is being read properly.

This simple plot, though, cannot really be used, since it's just a
mass of red points with no way to see surfaces or anything useful.

So I figured that the "pm3d" capability is probably what I need.

But if I type:
set pm3d
splot <filename>  with pm3d
I get a set of orthogonal axes, a pretty colour bar, and no points or
surfaces plotted.

I don't understand why I'm not seeing anything.  So I have two simple questions:

1. Why don't I see any points/surface plotted?
2. What commands do I need to issue in order to see the data?

  Doc Evans