Re: "sign" function

Thanks Denni, Brian and Kyle,

Anyway, still wondering to implement this function for multi-dimensional
arrays.. eg.

X= [time, level, lat] ---> Y= (X^2) * sign (X) , will result Y[time,
level, lat]

Any suggestion would be really appreciated.

Thanks

On Mon, Apr 7, 2014 at 3:38 AM, Dennis Shea <shea@ucar.edu> wrote:

> Untested
>
> undef("sign_matlab")
> function sign_matlab( X:numeric )
> ;
> ; Mimic Matlab 'sign' function
>
> ; sign(X) returns the sign of each element of 'X'
> ; 3 possible return values for non _FillValue elements: -1, 0, 1
> ; The return value type will be the same type as 'X'
> ;
> local typex, zero, onePos, oneNeg, result
> begin
> typex = typeof(X)
>
> zero = totype( 0, typex)
> onePos = totype( 1, typex)
> oneNeg = totype(-1, typex)
>
> result = X ; same size, shape and type as 'X'
>
> result = where(X.eq.zero, zero , result)
> result = where(X.gt.zero, onePos, result)
> result = where(X.lt.zerp, oneNeg, result)
>
> return(result)
> end
>
> ~
>
>
> On 4/6/14, 12:11 PM, Verena Lili wrote:
>
>> 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:
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>>>>
>>>>
>>>>
>>>
>>
>>
>>
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>>

-- 
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 13:03:18 2014