Re: usage of @LOC along y-direction

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Prasad,
Jaison has posted a fine answer, but I have one as well, that takes us
in another direction.  This lets us find the first, second, last, or any
other particular crossing of a value.

I decided to turn my answer it into an FAQ.  You can use the @EVNT
transform to count all of the times a variable reaches a certain value.  
Then
mask the variable so as to keep only the last crossing of the value, and 
use
@LOC on the masked variable.

Here is the FAQ, with an example worked out.

"How can I find the LAST occurence of an event or value?",  at
http://www.ferret.noaa.gov/Ferret/FAQ/analysis/location_of_last.html

Ansley Manke



Thoppil, Prasad IND wrote:

> Hi Ferret users,
>
> I would like to find the location of first isotherm, say 2C between the
> equator and 80S. To demonstrate clearly, 
> Assume that the contours look like this
>
> -------------------------- 2C ---------------- 60S (this is the location
> I want to get)
> -------------------------- 3C ---------------- 65S
> -------------------------- 4C ----------------- 70S 
> -------------------------- 3C ----------------- 75S
> -------------------------- 2C ----------------- 80S (not this)
>
> let iso2 = sst[y=80S:60S@LOC:2.0],
>
> iso2 would return the location of the 2C from south to north, that I get
> 80S. 
> Is there anyway that I can locate the first 2C isotherm from north to
> south instead of south to north?
>
> Thanks for your help,
>
> Prasad
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