[ncl-talk] converting string into a variable name

[Rick Brownrigg]

Tabish, David:

I see David has already replied regarding string references and file
variables.  Another thought I was working on was to use Lists. It's
probably overkill for your example; something like:

l = NewList("fifo")

ListPush(l, ispan(0,1000,1))
ListPush(l, ispan(1000,2000,1))
ListPush(l, ispan(2000,3000,1))

numl = ListCount(l)
do i = 1,numl
 var := ListPop(l)
 M = max(var)
 m = min(var)
 print(M+"       "+m)
end do

Rick



On Thu, Jan 26, 2023 at 7:15 AM Dave Allured - NOAA Affiliate via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Tabish, for your example, you could use a simple array instead of
> individually named variables.
>
> y = new (20, integer)
> y(1) = ispan(0,1000,1)
> y(2) = ispan(1000,2000,1)
> y(3) = ispan(2000,3000,1)
> --- etc. ---
>
> do i = 1,19
>  M = max(y(i))
>  m = min(y(i))
> --- etc. ---
>
> Note that NCL uses zero-based arrays, so this example ignores y(0) to keep
> your original indexing scheme from 1 to 19.
>
>
> On Thu, Jan 26, 2023 at 9:09 AM Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> Tabish, NCL string references work for file variables, but not for
>> in-memory variables.  See NCL reference manual, section "String references".
>>
>>
>> On Thu, Jan 26, 2023 at 8:46 AM Tabish Ansari via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Hi
>>>
>>> I have several systematically named variables that I want to refer to by
>>> generating the corresponding string via a loop. I'm able to generate a
>>> string that exactly matches the variable name but I'm unable to perform any
>>> operations over the variables by referring to the string.
>>>
>>> Here's my code:
>>>
>>> begin
>>> y1 = ispan(0,1000,1)
>>> y2 = ispan(1000,2000,1)
>>> y3 = ispan(2000,3000,1)
>>> y4 = ispan(3000,4000,1)
>>> y5 = ispan(4000,5000,1)
>>> y6 = ispan(5000,6000,1)
>>> y7 = ispan(6000,7000,1)
>>> y8 = ispan(7000,8000,1)
>>> y9 = ispan(8000,9000,1)
>>> y10 = ispan(9000,10000,1)
>>> y11 = ispan(10000,11000,1)
>>> y12 = ispan(11000,12000,1)
>>> y13 = ispan(12000,13000,1)
>>> y14 = ispan(13000,14000,1)
>>> y15 = ispan(14000,15000,1)
>>> y16 = ispan(15000,16000,1)
>>> y17 = ispan(16000,17000,1)
>>> y18 = ispan(17000,18000,1)
>>> y19 = ispan(18000,19000,1)
>>>
>>> do i = 1,19
>>>  var = "y"+tostring(i)
>>>  M = max($var$)
>>>  m = min($var$)
>>>  print(M+"       "+m)
>>> end do
>>>
>>> end
>>>
>>> I get a syntax error with this. Is it possible to achieve the same thing
>>> through some other syntax in an efficient way?
>>>
>>> Thanks a lot.
>>>
>>> Tabish
>>>
>>>
>>> -------------------------------
>>> Dr Tabish Ansari
>>> Research Associate
>>> Air Quality Modelling Group
>>> IASS-Potsdam
>>> Germany
>>>
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