Hi Patrick,
Yes, this kind of behavior is well known. ALINE is not reliable
particularly when used with a plot involving a time axis. Though it's
not as simple, it will always work to use the local coordinates.
Please see the notes in the documentation under the ALINE command:
http://porter.pmel.noaa.gov/Ferret/home/documentation/users-guide/appendix-c-ferret-specific-pplus-enhancements/ENHANCED-COMMANDS-DESCRIPTION%20#_VPID_756
This FAQ about putting symbols on a time-axis plot will be helpful in
constructing the coordinates you need for putting lines on top of a
time plot.
How
can I overlay symbols on a plot with a time axis?
Ansley
Brockmann Patrick wrote:
Hi all,
Sometimes drawing over a time plot is not as simple as it should be
with ferret.
I would like to draw a line in an absolute coordinate whatever the kind
of plot I draw.
Try.
!=============================
yes? go margins 2 2 2 2
yes? plot/nolab i[i=1:100]
yes? ppl pen 1,2
yes? ppl aline/nouser 1,-1,-1,1,-1
!=============================
==> it works and produces a small red line over the plot.
Now try
!=============================
yes? use monthly_navy_winds
yes? plot uwnd[i=@ave,j=@ave]
yes? ppl aline/nouser 1,-1,-1,1,-1
!=============================
==> Here nothing is drawn.
This is an old bug. Nothing new here.
Up to now, I haved used ideas from the script likealine (thanks to Mick
Spillane see
http://dods.ipsl.jussieu.fr/brocksce/ferret_bugs/likealine.jnl).
This script uses a time axis argument, finds its start and end and
computes the xslope and yslope
to finally uses a plot command.
This is not simple to draw a simple line but it works.
For exemple:
yes? plot/nolab uwnd[i=@ave,j=@ave,l=1:20]
yes? go likealine.jnl 0 100 0 100
draws a red line over across the viewport (0 100 are percentage
positions relative to the size of the viewport).
Now when I use a plot with 2 variables such as
yes? plot/nolab uwnd[i=@ave,j=@ave,l=1:20], vwnd[i=@ave,j=@ave,l=50:60]
yes? go likealine.jnl 0 100 0 100
it does not work anymore (I could compute a third variable but I want
to be as generic as possible).
So please, could it be possible a have a plot command with a /nouser
qualifier
or a ppl aline command working with time plots.
I would help us a lot to draw legends and all those silly small things
that are time consuming...
Thanks
Patrick
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