[ncl-talk] cross_corr_query
Dennis Shea
shea at ucar.edu
Mon Sep 12 16:13:21 MDT 2016
If you just want cross correlations with no lag use:
http://www.ncl.ucar.edu/Document/Functions/Built-in/escorc_n.shtml
On Fri, Sep 9, 2016 at 10:14 AM, Adam Phillips <asphilli at ucar.edu> wrote:
> Hi Kunal,
> Your use of esccr is correct as far as I can tell. It matches up with
> example #2 on the esccr documentation site:
> http://www.ncl.ucar.edu/Document/Functions/Built-in/esccr.shtml
> Adam
>
> On Fri, Sep 9, 2016 at 1:28 AM, Kunal Bali <kunal.bali9 at gmail.com> wrote:
>
>>
>> I have the data over the central arabian sea with the time steps = 31.
>>
>> With the given script, could you please let me know am I doing the
>> corss-correlation in a wright way
>>
>> ;*************************************************
>> ; corel_3.ncl
>> ;
>> ; Concepts illustrated:
>> ; - Calculating a two-dimensional correlation in time
>> ; - Reordering an array
>> ; - Copying attributes from one variable to another
>> ; - Copying coordinate arrays from one variable to another
>> ;
>> ;************************************************
>> ;
>> ; These files are loaded by default in NCL V6.2.0 and newer
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>> begin
>> ;************************************************
>> ; open file and read in variable
>> ;***********************************************
>> in1 = addfile("/media/Local Disk/NPL2/cross_corr_spatial/var1.nc","r")
>> in2 = addfile("/media/Local Disk/NPL2/cross_corr_spatial/var2.nc","r")
>>
>>
>> tmp1 = in1->DUD
>> tmp2 = in2->SRT
>> ;************************************************
>> ; reorder to get time as right most dimension
>> ;***********************************************
>> ts1 = tmp1(latitude|:,longitude|:,time|:)
>> ts2 = tmp2(latitude|:,longitude|:,time|:)
>> ;************************************************
>> ; calculate cross correlations
>> ;************************************************
>> maxlag = 3 ; set lag
>> ; note, the max lag should not be more than N/4
>>
>> ccr = esccr(ts1,ts2,maxlag) ; calc cross correlations
>>
>> ; copy meta data and coordinate variables using contributed functions
>> copy_VarAtts(ts1, ccr)
>> copy_VarCoords_1(ts2,ccr)
>> ;************************************************
>> ; plot the correlations
>> ;************************************************
>> ;************************************************
>> ;---Open workstation and change color map
>> wks_type = "png"
>> wks = gsn_open_wks(wks_type, "CCR_2_lag3")
>> ;************************************************
>>
>>
>> res = True ; make plot mods
>> res at gsnLeftString = ""
>> res at gsnRightString = ""
>> res at gsnAddCyclic = False
>> res at cnFillOn = True ; turn on color
>> res at cnFillPalette = "BlWhRe" ; set color map
>>
>> res at cnLinesOn = False ; turn off contour lines
>> res at cnLevelSelectionMode = "ManualLevels" ; manually set cn levels
>> res at cnMinLevelValF = -1. ; min level
>> res at cnMaxLevelValF = 1. ; max level
>> res at cnLevelSpacingF = .1 ; contour level spacing
>>
>> lag = 3
>> res at tiMainString = "Correlations at lag "+lag
>>
>> res at mpMinLonF = 59.8
>> res at mpMaxLonF = 69.8
>> res at mpMinLatF = 16.5
>> res at mpMaxLatF = 25.0
>>
>> plot = gsn_csm_contour_map(wks,ccr(:,:,lag),res)
>> ;************************************************
>> end
>>
>>
>>
>> Kunal Bali
>> Research Scholar
>> Radio & Atmospheric Science Division
>> CSIR - National Physical Laboratory
>> New Delhi - 110012
>> India
>>
>>
>>
>>
>>
>> On Fri, Sep 9, 2016 at 12:28 PM, Will Hobbs <will.hobbs at utas.edu.au>
>> wrote:
>>
>>> Kunal
>>>
>>>
>>>
>>> At least one of the data points in the arrays that you are correlating
>>> has every single value as ‘missing’ or the same value throughout. This
>>> usually occurs if your data includes some masked regions, e.g. ocean data
>>> with a spatial domain that includes land.
>>>
>>>
>>>
>>> Another possible valid condition would be precipitation data where one
>>> or more data points has been in drought for the entire time period, i.e. P
>>> = 0 throughout
>>>
>>>
>>>
>>> If you’re expecting you input data to include masked areas or similar
>>> physical conditions then it’s probably nothing to worry about (although
>>> that doesn’t mean you shouldn’t check). If you’re not expecting any missing
>>> values in your data then you may have a problem with your input arrays –
>>> but that’s not really an NCL problem.
>>>
>>>
>>>
>>> Will
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> *From: *<ncl-talk-bounces at ucar.edu> on behalf of Kunal Bali <
>>> kunal.bali9 at gmail.com>
>>> *Date: *Friday, 9 September 2016 at 4:46 PM
>>> *To: *"ncl-talk at ucar.edu" <ncl-talk at ucar.edu>
>>> *Subject: *[ncl-talk] cross_corr_query
>>>
>>>
>>>
>>> Dear NCL users,
>>>
>>> I am trying to plot the cross-correlation map. While doing this, I have
>>> baeen facing one error
>>>
>>> warning:esccr: Non-fatal conditions encountered: all missing or constant
>>> values
>>>
>>> Could anyone please let me know, how to fix it.
>>>
>>> Regards
>>>
>>> Kunal Bali
>>>
>>>
>>>
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>>>
>>
>>
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>
>
> --
> Adam Phillips
> Associate Scientist, Climate and Global Dynamics Laboratory, NCAR
> www.cgd.ucar.edu/staff/asphilli/ 303-497-1726
>
> <http://www.cgd.ucar.edu/staff/asphilli>
>
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