[ncl-talk] Possible bug with SPEI function? -website typos

[Dennis Shea]

The 'someone' is me.

The error is with the example(s). The hazards of duplication! I was in the
process of updating (ie: correcting) the documentation.

I will post back when all (hopefully) have been fixed.

D

On Mon, Feb 22, 2016 at 9:43 AM, Alan Brammer <abrammer at albany.edu> wrote:

> Benita,
>
> I see now that basically all these points apply to whoever wrote the
> examples and not to you.
>
> All examples on that page need to be edited.  I’m guessing someone did a
> find/replace on an older version of this function and didn’t check
> thoroughly.
>
> Also mistake on my part mixed up the order of these.
>  spei(prc, t, lat,len(k), False, 0)
>
>
>
> Alan.
>
>
>
>
> On 22 Feb 2016, at 11:31, Alan Brammer <abrammer at albany.edu> wrote:
>
>
> Hi Benita,
>
> Multiple things.
>  https://www.ncl.ucar.edu/Document/Functions/Built-in/spei.shtml
> At the top of the page.  " *Available in version 6.3.1
> <https://www.ncl.ucar.edu/prev_releases.shtml#6.3.1> and later. "*
>  So you can’t use the function yet, latest released version is 6.3.0.
> Which you’re using.
>
>
> Secondly,
> You can’t have variables and functions named the same thing.   When the
> function spei() is included, trying to define an array named spei is going
> to create problems.
>
> Line 16 won’t work in any language I know of.  Rename your variable so it
> doesn’t clash with the function name.
>
>
> Third.
> Again from the top link, spei() will expect 6 arguments and you only
> passed 4.
>
> Fourth.
> The specific error you’re getting is because NCL is trying to subscript
> the spei variable using False as you passed on line 16.  False isn’t a
> valid subscript.
>
> Fifth.
> Included edited lines below which should work once 6.3.1 is released.
> Though you will need to read in some temperature data as well. Read the
> functions documentation.
>
>
> ;;;;   Will need 6.3.1
>
>    f= addfile("pr_Amon_ensemble_historical_190001-200512.nc", "r")
>    prc    = f->pr                   ; pr(time,lat,lon)
>    printVarSummary(prc)
>
>    prc_dimnames = getvardims(prc)
>  time = lat= prc&$prc_dimnames(0)$ ;; get dimension coordinates without
> knowing dimension names
>   lat= prc&$prc_dimnames(1)$
>   lon= prc&$prc_dimnames(2)$
>
>   dimp   = dimsizes(prc)              ; # monthly precipitation values
>    ntim   = dimp(0)
>    nlat   = dimp(1)
>    mlon   = dimp(2)
>
>
>    len    = (/ 6, 12, 24 /)
>    klen   =  dimsizes(len)
>    spei_data    =  new((/klen,ntim,nlat,mlon/) ,float,prc at _FillValue)
>
>
>   t =  ….  ; spei needs a temperature variable same size as prc
>
>  do k=0,klen-1
>       spei_data(k,:,:,:) = spei(prc, t, len(k),lat, False, 0)
>   end do
>
>
>
> Good luck,
> Alan
>
>
>
> On 22 Feb 2016, at 11:11, Tam, Benita (EC/EC) <benita.tam at canada.ca>
> wrote:
>
> Hi,
>
> I am trying to calculate SPEI using the SPEI function in NCL with gridded
> data, but when I run the script, I get an error message saying that the
> subscripts must be one dimensional. This is expected for data for one
> location, but not for gridded data. My sample script is attached (it’s
> basically the same as the example provided with the function).
>
> NCL version: 6.3.0
> Script (see attached)
> Error message: fatal:Illegal subscript. Subscripts must be scalar or one
> dimensional vectors
> Url for netcdf data:
> http://ccds-dscc.ec.gc.ca/files/cmip5/pr/pr_Amon_ensemble_historical_190001-200512.nc
>
> Thanks,
> Benita
>
>
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