[ncl-talk] Taking ratio of precipitation dataset

[Dennis Shea]

b   = where(b.eq.0, b at _FillValue, b)
output = where((b.eq.0 .or. d(:,:,:).eq.0), (d-b), (d/b))

Using 'b' is more efficient then using 'b(:,:,:)'

===

ncl 49> output = ...

I suggest not be doing this interactively

Good Luck

On Wed, Jan 6, 2016 at 7:50 AM, amit timilsina
<timilsinaamit87 at huskers.unl.edu> wrote:
> Thank you so much
>
> I tried with following syntax.If it has properly considered first condition
> expression, the error "fatal:divide: Division by 0" would not have been
> appeared.
>
>
> ncl 49> output = where((b(:,:,:).eq.0 .or. d(:,:,:).eq.0), (d-b), (d/b))
>
> fatal:divide: Division by 0, Can't continue
>
> fatal:Div: operator failed, can't continue
>
> fatal:["Execute.c":8573]:Execute: Error occurred at or near line 49
>
>
>
> Regards,
>
> Amit Prasad Timilsina
>
> School of Natural Resources,UNL
>
>
>
>
> ________________________________
> From: Rick Brownrigg <brownrig at ucar.edu>
> Sent: Tuesday, January 5, 2016 7:41 PM
> To: amit timilsina
> Cc: ncl-talk at ucar.edu
> Subject: Re: [ncl-talk] Taking ratio of precipitation dataset
>
> Hi Amit,
>
> As was pointed out to me by one of my colleagues, you want to remove the
> calls to "any()" in the where statement I gave previously; otherwise, you'll
> still get differences everywhere.
>
> Rick
>
> On Tue, Jan 5, 2016 at 4:20 PM, Rick Brownrigg <brownrig at ucar.edu> wrote:
>>
>> Offhand, it seems like you want to use the where() function, rather than
>> an if/else coupled with any():
>>
>> http://ncl.ucar.edu/Document/Functions/Built-in/where.shtml
>>
>>
>> Something like (untested):
>>
>> output = where((any(b(:,:,:).eq.0)) .or. (any(d(:,:,:).eq.0)), d-b, d/b)
>>
>>
>> On Tue, Jan 5, 2016 at 4:10 PM, amit timilsina
>> <timilsinaamit87 at huskers.unl.edu> wrote:
>>>
>>> Respected all,
>>>
>>> I would like to take ratio and differences of variable precipitation(pr)
>>> in such way that if both the values for particular day is positive or
>>> greater than zero, I want to take ratio. If one of the values, either
>>> denominator or numerator, is zero, then I would like to take differences.
>>> Here is my code:
>>> ncl 0>
>>> a=addfile("pr_day_MRI-CGCM3_decadal2005_r1i1p1_20060101-20351231.nc","r")
>>> ncl 1> b=a->pr
>>> ncl 2>
>>> c=addfile("pr_day_MRI-CGCM3_rcp45_r1i1p1_20060101-20351231.nc","r")
>>> ncl 3> d=a->pr
>>> ncl 4> if (any(b(:,:,:).eq.0)) .or. (any(d(:,:,:).eq.0)) then
>>> ncl 5> output = (d-b)
>>> ncl 6> else
>>> ncl 7> ouput = d/b
>>> ncl 8> end if
>>>
>>> This output gives me only differences, not a combination of both. Is it
>>> possible to put any flag to know whether we have considered differences or
>>> ratio at each grid level? I have attached printVarSummary for further
>>> information.
>>>
>>> Thank you in advance
>>>
>>>
>>>
>>> Amit Prasad Timilsina
>>> PhD student
>>> School of Natural Resources,UNL
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> ncl-talk at ucar.edu
>>> List instructions, subscriber options, unsubscribe:
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>>>
>>
>
>
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