Re: problem of the extenal function -- lsl_lowpass

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi,
The problem that Ferret is having is in knowing that you want
to compute the lowpass filter for the data using a range of times,
and then shade it at just one time. The command

yes? shade/l=10 lp20

is saying to Ferret that it should apply the region /L=10 to the
whole expression. It tries to compute the filter using only the
data at L=10, and it cannot do that.

If you change your definition of TTW20 to

 TTW20 = TEMPC[I=70:120,J=1:50,K=3,L=1:1826] 

Then Ferret can use the range of time that is needed to compute
the result. Your shade command should give you what you want.

Please don't worry about your English. We always want people to
ask their questions. You explained the question well, by showing
what your grid is like and by telling us the commands that you used.

Ansley

alutw wrote:

>Hi all: 
> I got a problem for using lsl_lowpass function to 
>filter my 2D  daily data. 
>
>My dataset and varibles as following 
>
>=============================================================================
>   1> ./st.cdf  (default) 
>name     title                             I        J        K         L 
>SALTC    Salinity on z-level              1:160    1:70      1:12      1:1826 
>TEMPC    Temperature on z-level           1:160    1:70      1:12      1:1826 
>=============================================================================
>    TTW20 = TEMPC[I=70:120,J=1:50,K=3] 
>    LP20 = LSL_LOWPASS(TTW20,365,365) 
>=============================================================================
>
>While i shaded lp20 , " command : "yes? shade/l=10 lp20" , 
>I got  error message as following : 
>
>=============================================================================
>Bailing out of external function 
>"lsl_lowpass": 
>       LSL_FILTER: The filter span must be less than or equal to the number 
>of points 
>**ERROR: : error in external function 
>=============================================================================
>
>Actually,I have no idea where I went wrong. 
>I'd like to know how the lsl_lowpass function to be apply for 2D or 3D data. 
>
>Teach me to solve this problem,plz. 
>Sorry for my poor English. 
>Thanks a lot. 
>
>
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