[ncl-talk] "sum" and "avg" functions without ignoring missing values

[Rashed Mahmood]

Thanks Dave, that is exactly what I was looking for...


On Fri, Nov 24, 2017 at 11:46 AM, Dave Allured - NOAA Affiliate <
dave.allured at noaa.gov> wrote:

> Rasheed,
>
> I think dim_cumsum and dim_cumsum_n with opt=0 are intended for this
> purpose.  There is no corresponding function for "avg".  However, simply
> dividing the result array from dim_cumsum by N should give the correct
> array result, with no extra "if" or "where" statement.
>
> --Dave
>
>
> On Fri, Nov 24, 2017 at 12:29 PM, Rashed Mahmood <rashidcomsis at gmail.com>
> wrote:
>
>> Hi Arne,
>>
>> Thanks for trying to answer the question, however, the things you
>> mentioned would add confusion and possibly wrong results.
>> Actually I know how to achieve what I want using a do loop. For example,
>> let us say we have variable a = (ntimes,nlevel,nlat,nlon) and we want to do
>> sum over time domain which can easily be done using: (dim_sum_n(a,0)), Now
>> the results would be sum over all non-missing values of
>> time1,time2,time2...timeN, which is correct.
>>
>> But if I want to do sum ONLY when all of the values of
>> time1,time2,time3...timeN are non-missing then we can do this:
>>
>>  dimz = dimsizes(a)
>>  b      = new(/dimz(1),dimz(2),dimz(3),float)
>>  b at _FillValue = a at _FillValue
>>
>>   b(:,:,:) = 0.
>>   do n=0,dimz(0)-1
>>        b = b+a(n,:,:,:)
>>   end do
>>
>> I just wanted to avoid the loop and use the "sum" function for
>> efficiency. I hope this clarifies the question a bit more.
>>
>> Cheers,
>> Rashed
>>
>>
>> On Fri, Nov 24, 2017 at 3:01 AM, Arne Melsom <arne.melsom at met.no> wrote:
>>
>>> Hi!
>>> Since 'music piano' replied, I thought I might chime in ;)
>>> I'm pretty sure that no option(s) to functions allow you to do what you
>>> want.
>>> So you'll need to write alternative functions yourself (perhaps not what
>>> you consider 'an easy way'...)
>>> You may use something like
>>>
>>> aDim = dimsizes(a)
>>> orgFill = a at _FillValue
>>> newFill = -min(abs(a)) - 1    ; make sure newFill is out of range and <0
>>> if (newFill .eq. orgFill) then  ; newFill must be different from orgFill
>>>   newFill = newFill - 1
>>> end if
>>> newVar = ndtooned(a)
>>> newVar at _FillValue = newFill
>>> indx = ind(ismissing(newVar))
>>> newVar(indx) = orgFill
>>> newa = onedtond(newVar,aDim)
>>>
>>> ...and, if you later want to restore:
>>> a = newa
>>> a at _FillValue = orgFill
>>>
>>> Hope this helps/clarifies!
>>> Best regards,
>>> Arne
>>>
>>>
>>> 2017-11-24 1:49 GMT+01:00 Rashed Mahmood <rashidcomsis at gmail.com>:
>>>
>>>> Hello all,
>>>> I am just wondering if there is an easy way to tell the "sum" and "avg"
>>>> functions NOT ignore the missing values. Below lines clarify my question
>>>> where I would like to see same values for c and d:
>>>>
>>>> ncl 0> a = (/(/-9.,2,-9./),(/1,-9.,2./)/)
>>>> ncl 1> a at _FillValue = -9.
>>>> ncl 2> c = (a(0,:)+a(1,:))
>>>> ncl 3> d = dim_sum_n(a,0)
>>>> ncl 4> print("  "+c+ " ... "+d)
>>>> (0)       -9 ... 1
>>>> (1)       -9 ... 2
>>>> (2)       -9 ... 2
>>>>
>>>> Thanks,
>>>> Rashed
>>>>
>>>
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