labeling a plot in a viewport

[Hein Zelle <zelle@xxxxxxx>]

Dear Ferret users and developers,

As a followup question on the previous one, I'd like to know how to
use 'user' and 'global' coordinates when labelling a plot that is in a
viewport which takes up only part of the page. Here's what I want to
do: I have divided my page into 12 viewports, one for each month, just
like the landscape3x2 script. (If anyone is interested, I now have a
portrait2x6 script). I make a contour plot in the first viewport of,
say, the january climatology.

So far so good, but the title of the plot doesn't really fit in such a
small viewport so I leave it off. Instead, I want to plot a label with
'January' within the area of the plot. Ideally, I want this label to
appear within a white box, so it doesn't run through the contour
lines. The questions I ran into:

- How do I specify label coordinates relative to the axes of the plot
  if I don't know the data along the axis? It's a general script, so I
  cannot assume that the left bottom corner is always 120E,30S.

- How can I make a white box around a label? I was thinking of using a
  very small 'label' viewport for this, but just as with the label I
  don't know how to position this 'subviewport'. 

- I draw the title of the plot in a 13th viewport at the bottom of the
  page, specified with define viewport /axes. I found out that
  relative coordinates (0.5,0.5 for a centered label) only work after
  you plot something in that viewport. How do I 'initialize' a
  viewport so that these relative coordinates work, without actually
  plotting something in it?

I will attach the two scripts to this mail so you can check them
out. 12month.jnl defines the viewports (the 'label' viewports are
commented out), 12plot.jnl is a general script to plot 12 months of a
climatology.

I hope someone can help with this, the result already looks pretty
good but could be perfected some more.

     Hein Zelle

>-----------------------------------------------------------------<
    Hein Zelle
    Dept. of Oceographic Research
    KNMI, The Netherlands
    work:        zelle@knmi.nl     http://www.knmi.nl/~zelle
    private:     hein@icce.rug.nl  http://www.icce.rug.nl/~hein
    Phone:       +31 (0)30 2206704
>-----------------------------------------------------------------<
--------------------------------------------------------------
Zie ook/see also: http://www.knmi.nl/maildisclaimer.html 
\cancel mode verify

! make a plot for each of the 12 months of variable $1

! first check arguments
query/ignore $1%<Usage: 12plot [var] [title], [var] must have 12 time frames%

! metafile on for plotting
set mode metafile

! set a reasonable window aspect ratio for paper
set window /aspect=1.25         ! us letter = 1.294

! set 12 viewports + 1 for the title
go 12month

! loop over each month
! the label should really be plotted in a white box instead of across the plot
repeat /l=1:12 (set viewport `l`; go margins 0.2 0.6 1.0 0.4; contour /set_up /nolab /levels=21c $1; ppl contour; label/nouser 0.2,0.1,-1,0,0.12 "@p7Month `l`" )

! plot the title centered at the bottom of the page in a larger font
set viewport 13
! this should be 0.5,0.5 but that doesn't work as I don't plot anything
! in the viewport. 5.5 is an estimated value which is not robust.
label/nouser 5.5,0.5,0,0,0.2 $2%"Climatology"%

! stop metafile mode
cancel mode metafile

! restore verify mode
set mode /last verify
! define 12 viewports for later use, arranged in 2 columns of 6.
! intention is to use this for plotting one month of data in each plot,
! to give a climatological overview.

define viewport /xlimits=0,0.5 /ylimits=0.1,0.25     6
define viewport /xlimits=0,0.5 /ylimits=0.25,0.4     5
define viewport /xlimits=0,0.5 /ylimits=0.4,0.55     4
define viewport /xlimits=0,0.5 /ylimits=0.55,0.7     3
define viewport /xlimits=0,0.5 /ylimits=0.7,0.85     2
define viewport /xlimits=0,0.5 /ylimits=0.85,1.0     1
define viewport /xlimits=0.5,1 /ylimits=0.1,0.25     12
define viewport /xlimits=0.5,1 /ylimits=0.25,0.4     11
define viewport /xlimits=0.5,1 /ylimits=0.4,0.55     10
define viewport /xlimits=0.5,1 /ylimits=0.55,0.7     9
define viewport /xlimits=0.5,1 /ylimits=0.7,0.85     8
define viewport /xlimits=0.5,1 /ylimits=0.85,1.0     7

! define 12 'corner' viewports to plot the label into
!  define viewport /xlimits=0,0.08 /ylimits=0.1,0.115   1l
!  define viewport /xlimits=0,0.5 /ylimits=0.25,0.4     2l
!  define viewport /xlimits=0,0.5 /ylimits=0.4,0.55     3l
!  define viewport /xlimits=0,0.5 /ylimits=0.55,0.7     4l
!  define viewport /xlimits=0,0.5 /ylimits=0.7,0.85     5l
!  define viewport /xlimits=0,0.5 /ylimits=0.85,1.0     6l
!  define viewport /xlimits=0.5,1 /ylimits=0.1,0.25     7l
!  define viewport /xlimits=0.5,1 /ylimits=0.25,0.4     8l
!  define viewport /xlimits=0.5,1 /ylimits=0.4,0.55     9l
!  define viewport /xlimits=0.5,1 /ylimits=0.55,0.7     10l
!  define viewport /xlimits=0.5,1 /ylimits=0.7,0.85     11l
!  define viewport /xlimits=0.5,1 /ylimits=0.85,1.0     12l


! define the 'title' viewport as the 13th.
! I don't know how to plot the global title otherwise, as changing
! the viewport or cancelling it will erase anything previously drawn there.

define viewport /axes /xlimits=0,1 /ylimits=0,0.1    13