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Re: [ferret_users] Correlation between one point and 2D spatial data



Hi,
I think your script looks correct, if the data are the right shape.  After opening your dateasets, look at the output of "show data" for a first check of this.

You want to get a result in XY, the correlation in time between your single time series, and the time series at each XY location in the gridded dataset.  A simple example of this would look like this:
yes? use coads_climatology
yes? let p = sst
yes? let q = airt[x=180,y=0]
yes? go variance
yes? shade correl
The error about improperly specified region is coming from the SHADE command; it's saying that CORREL is not 2-D. 
! Check the grid of the 2-D variable, and then the time series.
! plot the data field at one time, and the time series at one location.

yes? shade ssh[L=1]
yes? plot ssh[x=180,y=0]   ! or at some location where there is data

! check the grid of the time series data
yes? plot uvel

The STAT  and LIST commands are also useful to look at the number of values in variables and whether there is data present.

-Ansley


On 1/14/2016 11:07 PM, 'Iskhaq Iskandar' via _OAR PMEL Ferret Users wrote:
Dear Ferret users,

I am trying to compute a correlation between an observed current at one location (1D data: varies in time only) with SSH of a basin-wide region (2D data in x,y and time).

What I did is something like this:

-------------------
use daily-ssh.nc
use daily-current.nc
set mem/size=600

def axis/t=1-jan-2009:19-May-2010:1/unit=days tday
let ssh = sla[d=1, gt=tday]
let uvel = u[d=2, gt=tday]

let p = uvel
let q = ssh
go variance

shade correl
!
can data/a
can var/a
can mem
--------------------

But I got an error like:

-------
 *** NOTE: Ambiguous coordinates on X axis: P*Q-P*Q + 1
 *** NOTE: Ambiguous coordinates on X axis: Q*MASK_PQ
 *** NOTE: Ambiguous coordinates on X axis: COVAR / (P_VAR_MASK*Q_VAR_MASK)^.5
 *** NOTE: Ambiguous coordinates on X axis: P_DEV_MASK * Q_DEV_MASK
 **ERROR: dimensions improperly specified: must be a 2D region
--------

If I change between P and Q, I will get an error like:

--------
*** NOTE: Ambiguous coordinates on X axis: P*Q-P*Q + 1
 *** NOTE: Ambiguous coordinates on X axis: Q*MASK_PQ
 *** NOTE: Ambiguous coordinates on X axis: COVAR / (P_VAR_MASK*Q_VAR_MASK)^.5
 *** NOTE: Ambiguous coordinates on X axis: P_DEV_MASK * Q_DEV_MASK
 **ERROR: inconsistent sizes of data regions: X axis
          Q has 3 points (I=0:2)
          _expression_ has 301 points (I=001:301)
---------

Do you have any suggestion?
Thank you for help.

Best regards,
Iskhaq



---------------------------------------------------------------- Dr. Iskhaq Iskandar Jurusan Fisika, Fakultas MIPA Universitas Sriwijaya Kampus Inderalaya, Ogan Ilir (OI) Sumatra Selatan, 30662 INDONESIA Phone: +62 (711) 580743 Fax: +62 (711) 580268 E-mail: iskhaq.iskandar@xxxxxxxxx http://iskhaq.wordpress.com/ ----------------------------------------------------------------


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