Re: [ferret_users] How to control contours interval?

[Goran Georgievski <goran@xxxxxxx>]

Hi William, 

thank you for your reply. I was aware about SIZE and SPACING qualifiers. 
Playing with then gives a little better results, indeed..., but still not 
satisfactory.  

I knew that contour/fill and fill is pretty much the same and that I could use 
ppl contour/ov, however note that levels are similar but not exactly the 
same. It is:

contour/fill/levels=(-1600,-800,200)(-800,-300,100)(-300,300,25)(300,800,100)
(800,1600,200)

and

contour/size=.1/levels=(-1600,-800,200)(-800,-300,100)(-300,300,25)
(300,800,100)(800,1600,200)del(0)

in the latter case there is additional del(0), but none in the first issue of 
the command. The reason for that is if I put  del(0) in the fill command 
levels, then shakey would not write simetric values below colorbar. On the 
other hand using 0 level with contour command makes figure look noisy. 

Acctualy, reducing number of levels and keeping non-continuous key seems to 
give the most satisfying results.  

Thank you for your input.
Best regards,
Goran

On Thursday 24 November 2005 16:41, William S. Kessler wrote:
> Hi Goran -
>
> It is possible to "influence" the number of contour levels ....
> "control" would be too strong a word. The pplus graphics code uses an
> algorithm to avoid contour labels overwriting contour lines, so where
> the lines are dense it omits labels. There are several interacting
> methods to influence the number of labels drawn, see the
> documentation for the qualifiers:
>
> CONTOUR/SIZE/SPACING
>
> Reducing SIZE and SPACING should get you more labels. In my
> experience, SPACING acts very non-linearly. Reducing the default 5
> (inches) makes little difference until somewhere between 2 and 3,
> then suddenly as the value is made smaller there will be many more
> labels.
> Also note that if you are drawing the same contour lines over a FILL
> plot, it is not necessary to write out the CONTOUR command as you do
> here. Simply:
>
> PPL CONTOUR/OVER
>
> or do
>
> FILL/LINE/KEY to get the whole thing in one command (note that FILL
> is an alias for CONTOUR/FILL)
>
> Another useful method is to use few FILL levels (say no more than 7
> or 8), with a non-continuous key. Then overlay finer contour lines.
> The viewer can easily see the coarse, discrete color levels, then use
> the contours to distinguish the finer details.
>
> A desperation move to get more labels is to overlay separate contour
> plots for each level. That thwarts the algorithm to prevent label
> overwriting, and the results may not be pretty, but it will produce
> more labels.
>
> Billy K
>
> On Nov 24, 2005, at 12:45 AM, Goran Georgievski wrote:
> > Hello ferret users,
> >
> > Is it possible to have more control over labels used for contour
> > intervals?
> > I have the following script for producing attached plot (please
> > have a look at
> > the attached file: giants_pme_anom.gif)
> >
> > contour/fill/levels=(-1600,-800,200)(-800,-300,100)(-300,300,25)
> > (300,800,100)
> > (800,1600,200)/key=continous/nolab/set_up pme-pme_ctrl
> > ppl axlint,2,2
> > ppl axlsze,0.2,0.2
> > ppl shakey 1, 0, 0.14, 6, , , 1.15, 9.25, 0.5, 0.7
> > ppl fill
> > contour/size=.1/levels=(-1600,-800,200)(-800,-300,100)(-300,300,25)
> > (300,800,100)(800,1600,200)del(0)/nolab/ov pme-pme_ctrl
> > go land
> >
> > I have several anomaly patterns that I want to compare (values
> > spans from
> > -1600 to 1600), but for the attached figure values spans form -250
> > to 250.
> > However, altough values are in that range (-250, 250), when I plot the
> > contour only labels for 25 and -25 isolines appear, even though I
> > used levels
> > qualifier. I would expect that not only 25 levels are marked, but also
> > 25,50,75 etc... How to do that?
> >
> > Thank you for your support,
> >
> > Goran
> >
> >
> >
> > --
> > Goran Georgievski
> > ICBM, Physical Oceanography (Theory), University of Oldenburg
> > PO Box 2503, D-26111 Oldenburg, Germany
> > Tel: +49-(0)441-798-4061, Fax: +49-(0)441-798-3404
> >
> >
> >
> > <giants_pme_anom.gif>