[ncl-talk] Retrieving variables from lists.

[Kyle Griffin]

So are you referencing the ListIndex function?

https://www.ncl.ucar.edu/Document/Functions/Built-in/ListIndex.shtml

>From the list section of the manual...
https://www.ncl.ucar.edu/Document/Manuals/Ref_Manual/NclVariables.shtml#ListVariables

I usually try to construct lists with ListPush and ListPop...this is more
consistent with how lists are intended to work in other languages (I know
it from Java, but I'm sure there are others) where they are intended to
host any number of data types, but the *order* of the items is what is
relevant. You declare the list to be "first-in, first out" or "last-in,
first out" and push things in or pop things out of the list, which will
return items as intended. You can also get the index and pull it out as an
object from an array would as well, although this is not as simple.

Personally, I've had a few issues with how variables are treated once
pushed/popped from a list last time I tried to use the feature, but I can't
recall what the specific issue was off the top of my head. I'd be curious
as well to hear more from those who work with lists in NCL more often.


Kyle

----------------------------------------
Kyle S. Griffin
Department of Atmospheric and Oceanic Sciences
University of Wisconsin - Madison
Room 1421
1225 W Dayton St, Madison, WI 53706
Email: ksgriffin2 at wisc.edu


On Mon, Aug 4, 2014 at 4:26 PM, Brammer, Alan P <abrammer at albany.edu> wrote:

> Dear NCL talk,
>
> I never really utilise lists in NCL as I struggle with how they work.
>  Hopefully this mundane example can help clarify my desires and maybe find
> a solution.  Or maybe I’m trying to use them in a way they were not meant.
>
> I have a function “list_test” as below, and in my script I call that and
> depending on the argument will get a return list back, that all works
> great.  My question is how do I get say variable "x" out of the returned
> list.  I can assume its location in the list but that seems risky and
> unfriendly for development.
>
> Can I get an array of the variables names within a list so I can then pull
> “x” out using ListIndex or something similar.
> Is there a listIndex where I pass the variable name instead of the
> variable.
> Do I have to attach a list of names and index locations to the list so I
> know where things are in it?
>
>
> As always these example scripts are exemplifying much more complicated
> code therefore hard coding the answer isn’t really the solution I want.
>
>
> Thanks in advance,
>
> Alan.
>
>
>
>
> undef("list_test")
> function list_test(a:logical)
> local k, x, y, x, retlist
> begin
>   if(a)
>       x = fspan(0,10, 11)
>       y = fspan(100,120,11)   ;  just random arrays of numbers.
>       z = ispan(0,100,1)
>       retlist = [/ x, y, z /]
>   else
>       k  = ispan(10,15, 1)
>       x = fspan(10,20, 11)
>       y = fspan(200,220,11)
>       retlist = [/ k, x, y /]
>   end if
>
>   return(retlist)
> end
>
>
>
>
> begin
>
> firstlist = list_test(True)
> print(firstlist)
>
> ; xind = ind( firstlist .eq. “x”   )   ;;; is there some way for this to
> work?  firstlist at variable ? ?
>
> secondlist = list_test(False)
> print(secondlist)
>
> ; xind = ind( secondlist .eq. “x”   )   ;;;
>
> end
>
> _______________________________________________
> ncl-talk mailing list
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20140804/e53e6198/attachment.html