Re: [ferret_users] $ppl$yorg and friends

[Ryo Furue <furue@xxxxxxxxxx>]

Thank you, Ansley, for the detailed explanation.

| The difference is in how the different commands use these symbols,
| not in the values at different times.  The values are the same
| whether after set_up is issued, or after a plot command is
| finished.

I see.  In other words, the "nouser" coordinates differ from
command to command. 

After set_up is issued and before the plot command is finished,
the lower-left corner is (xorg, yorg).  This applies to SHAKEY.

On the other hand, for the LABEL command, the lower-left corner
is (0,0), not (xorg, yorg), in the nouser coordinates.

The width and height of the plot, however, are xlen and ylen
for both cases.

That seems to mean that we should document these things for each
command that handles nonuser coordinates.

| LABEL positions the labels relative to the origin, as it is (often)
| used for positioning labels inside the box formed by the coordinate
| axes, and it can be used with USER coordinates, to position a label in
| terms of world coordinates such as degrees.

As an aside, USER coordinates are often convenient for LABEL,
but you prefer NOUSER ones when you want to place your labels
at the same locations (in the paper coordinates) regardless
of the size (in USER coordinates) of the plotting region.

Regards,
Ryo