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Re: [ferret_users] Interpolating in places given by a variable.Was:Creating custom variable along z axis.

Hi Cesar,
This can be found in the Users Guide under "sigma coordinate data".  The function to use is the ZAXREPLACE function, where you will define a Z axis in terms of height and use the function to put your "levels" data onto that. I've just added some more index entries and cross-references to the Users Guide, so the information is be easier to find.  There are several examples, so give it a try and write back here to the users list if you need  any help.


Thank you for your help.
It worked perfectly.

I have another question:

I have a variable "modulus" that gives me the wind in m/seg for I,j,k.
But the k coordinate comes in 'sigma levels' and I want it interpolated
at some heights in meters.
The values for al sigma levels are given by the variable altz, and this is a variable that depends on I,j (on K too).

So, I can get the sigma level for 60 m for each I,j with the
Following command:

let micooz=mialtz[z=2:6@loc:60]

But now, I do not know how to use it to extract the interpolation of modulus in the sigma levels specified in micooz.

Thank you very much,


-----Original Message-----
From: Jaison Kurian [mailto:jaison@caos.iisc.ernet.in] 
Sent: 26 September 2006 12:26
Cc: ferret_users@noaa.gov
Subject: Re: [ferret_users] Creating custom variable along z axis.

Hi Cesar,
           You can use ZSEQUENCE function to define a 1D array 
(on Z-axis). From user manual, Ch3 Sec2.3.25 :

data from the argument into a 1-dimensional line of data on an ABSTRACT 

So try something like this,

    yes? let f2s = ZSEQUENCE({1, 0, 0, 0, 0})

Now f2s will be on a "ABSTRACT" axis. If you want to assign a proper Z
axis, then 

    yes? define axis/z=1:5:1 zax
    yes? let f2s_z = f2s[gz=zax@ASN]  ! @ASN regridding just assigns the
                                      !       axis 

Regarding the error message you got :

    let f2s= {1, 0, 0, 0, 0} --> will define f2s on X-axis (the default
way) and it does not have any other valid axes. So when you try
    set variable/grid=migrid f2s

there is a mismatch...like variable have only X-axis and the destination
grid does have only Z-axis. This way it won't work. That is why Ferret 
warns that "Grid for a user-defined variable is implied by its definition"
If you want to remap from X to Z axis, you have to use RESHAPE function.

In the solution i suggested earlier, the variable is defined on "Z" axis
and the regridding is done on Z-Axis ..so it is consistent.

Hope This Helps,



On Tue, 26 Sep 2006, TEJEDA HERNANDEZ, CESAR wrote:



I want to create a variable with these values:


let f2s= {1, 0, 0, 0, 0}


But along z axis (not x). 


This statements are not useful after the definition:


yes? define axis /z=1:5:1 zaxis

yes? define grid /z=zaxis migrid

yes? set variable/grid=migrid f2s

 **ERROR: invalid command: cannot specify grid for f2s

          Grid for a user-defined variable is implied by its definition


¿Any hint?


Thanks in advance.







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Ansley Manke, NOAA/PMEL   ansley.b.manke@noaa.gov
7600 Sand Point Way NE, Seattle WA
Phone 206-526-6246,  FAX 206-526-6744

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