Re: [ferret_users] Vector plot: force maximum?

["William S. Kessler" <william.s.kessler@xxxxxxxx>]

Whether or not that works (I haven't looked at your code in detail),  
generating false data seems a bad idea. What if you forgot that's what  
you were doing? What if the audience at a talk or reader of a paper  
missed that crucial point? What if you computed any further statistics  
using the false data?

I would do one of three things:
1. plot the log of the data (or the square root, not uncommon in  
plotting vectors with a large range of values)
2. use your mask to blank out the too-high data: the holes are real.
3. use PLOT/VLIMITS to limit the height of a (line) plot

One man's opinion.

Billy K

On May 5, 2009, at 11:08 AM, Steve Cousins wrote:

> Long time!
>
> I have a dataset with U and V velocity components. There is a river  
> that comes into the domain that has high values that I want to  
> limit. What I have done so far is:
>
> let wind_mask = IF ABS( (u^2 + v^2)^.5) LT .08 THEN 1
> let u2 = u * wind_mask
> let v2 = v * wind_mask
>
> vector/xskip=2/yskip=2 u2,v2
>
> This works but it puts holes in the data. What we'd like is to have  
> it so if a speed is greater than 8 cm/sec we scale it down to 8 cm/ 
> sec so the grid doesn't have holes in it and we can still see the  
> direction.
>
> Thinking about this as I type (don't try this at home!) I think I  
> need something like:
>
> let wind_mask = IF ABS( (u^2 + v^2)^.5) LT .08 THEN 1 ELSE
>                  (.08 /  ABS( (u^2 + v^2)^.5))
>
> ... testing ...
>
> It works! Ferret is Great! Hold on. I think it is working. It fills  
> in the gaps. It *looks* like the scaling is correct...
>
> Is there a better way to do this?
>
> Thanks,
>
> Steve
> ______________________________________________________________________
> Steve Cousins, Ocean Modeling Group    Email: cousins@xxxxxxxxxxxxxx
> Marine Sciences, 452 Aubert Hall       http://rocky.umeoce.maine.edu
> Univ. of Maine, Orono, ME 04469        Phone: (207) 581-4302