Re: "sign" function

This is not what I intended to do..

let's say I have a simple array X =(/-5,-2,-1,5,2,1/)

thus Y= X^2 * sign (X)

will produce: Y=(/-25,-4,-1,25,2,1/)

or M= sqrt (Y) * sign (Y)

would be M = (/-5,-2,-1,5,2,1/)

The main things are that I need to retain the + or - sign in the values. I
need this function for my complex number analyses. Then another question
arising, how if my arrays contain more than one dimension let' say 3D.
 I'was wondering befored whether a similar function called as "sign" which
is availabel in Matlab is available in NCL.

Thanks

On Mon, Apr 7, 2014 at 2:52 AM, Kyle Griffin <ksgriffin2@wisc.edu> wrote:

> You might try something like this...
>
> Given that x = (/time, level, lat, lon/) as you specified in your email -
> or honestly, any dimension should work fine
>
> signx = where(x.eq.0,x@_FillValue,x)
> signx = x/abs(x)
> signx = where(ismissing(signx),0,x)
> signx = where(ismissing(x),x@_FillValue,signx)
>
> The middle line alone would work if you knew none of your values were
> exactly zero, but would cause divide-by-zero errors if there were zero
> values. Since I believe the where function evaluates the entirety of both
> the 'true' and 'false' arrays, you would run into the same problem with
> doing a x/abs(x) in the where function if you don't set all the zero values
> to missing first. This also has a problem, though, in that it will end up
> setting all missing values to '0' sign in the third line, but we can fix
> that with the fourth line and simply copy the missing value locations out
> of the original data.
>
> I haven't tested these lines of code, but I think they should get the job
> done.
>
> Let the list know how this works out!
>
>
> 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@wisc.edu
>
>
> On Sun, Apr 6, 2014 at 9:59 AM, Verena Lili <verena.prick@gmail.com>wrote:
>
>> The problem is following:
>>
>>
>> ncl 0>
>> ncl 1> function sign( X )
>> ncl 2> begin
>> ncl 3> if X.eq.0 then
>> ncl 4> result = 0
>> ncl 5> else
>> ncl 6> if X.gt.0 then
>> ncl 7> result = 1
>> ncl 8> else
>> ncl 9> result = -1
>> ncl 10> end if
>> ncl 11> end if
>> ncl 12> return( result )
>> ncl 13> end
>> ncl 14>
>> ncl 15> a=(/-2,-3,-4,4,5,6-1/)
>> ncl 16>
>> ncl 17>* b=(a^2)*sign(a)*
>> *fatal:Conditional statements (if and do while) require SCALAR logical
>> values, see all and any functions*
>> *fatal:Execute: Error occurred at or near line 11*
>>
>> *fatal:Execute: Error occurred at or near line 17*
>>
>> Any subroutine that can work as global "sign" function in ncl and can be
>> used for multidimensional arrays? e.g.
>>
>> X= [time, level, lat, lon]
>>
>> y= (X^2) * sign (X)
>>
>> Thank you.
>>
>>
>>
>> On Thu, Apr 3, 2014 at 3:30 AM, Verena Lili <verena.prick@gmail.com>wrote:
>>
>>> Thanks Brian!
>>>
>>>
>>> On Wed, Apr 2, 2014 at 6:50 PM, Brian Medeiros <brianpm@ucar.edu> wrote:
>>>
>>>> You could write that function:
>>>>
>>>> function sign( X )
>>>> begin
>>>> if X.eq.0 then
>>>> result = 0
>>>> else
>>>> if X.gt.0 then
>>>> result = 1
>>>> else
>>>> result = -1
>>>> end if
>>>> end if
>>>> return( result )
>>>> end
>>>>
>>>> .brian
>>>>
>>>>
>>>> On Apr 2, 2014, at 10:40 AM, Verena Lili <verena.prick@gmail.com>
>>>> wrote:
>>>>
>>>> Hi NCL,
>>>>
>>>> Is there any function in NCL similar like `"*sign" *function in Matlab?
>>>>
>>>> --
>>>> Regards,
>>>> Dr. Verena.
>>>> School of Marine and Atmospheric Sciences
>>>> Stony Brook University
>>>> homepage: http://www.somas.stonybrook.edu/
>>>> _______________________________________________
>>>> ncl-talk mailing list
>>>> List instructions, subscriber options, unsubscribe:
>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Regards,
>>> Dr. Verena.
>>> School of Marine and Atmospheric Sciences
>>> Stony Brook University
>>> homepage: http://www.somas.stonybrook.edu/
>>>
>>
>>
>>
>> --
>> Regards,
>> Dr. Verena.
>> School of Marine and Atmospheric Sciences
>> Stony Brook University
>> homepage: http://www.somas.stonybrook.edu/
>>
>> _______________________________________________
>> ncl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>

-- 
Regards,
Dr. Verena.
School of Marine and Atmospheric Sciences
Stony Brook University
homepage: http://www.somas.stonybrook.edu/

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Received on Sun Apr 06 12:11:56 2014