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Re: [ferret_users] ppl aline or plot/nouser

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:


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?


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.

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...


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