# Re: Correlation Question

From: Nkese Mc Shine <Nkese.McShine_at_nyahnyahspammersnyahnyah>
Date: Thu May 02 2013 - 08:48:23 MDT

Dear All,

I probably was not clear on what I wanted to do. I would like to correlate one(1) month sst(lat,lon,time) with 1 month of precipitation which is actually one(1) value precip(time) and I wanted the correlation to be (lat,lon) so that it can be plotted on a map. So what I understand is this can not be done. Since my precipitation data has only the time dimension then using the pattern_cor() can not be used either because the output is (time) only and my precipitation data would have to also contain lat and lon.

If there any other suggestions to what I may be able to do, please let me know. Thank you for all your help.

Regards,
Nkese.
________________________________________
From: Dennis Shea [shea@ucar.edu]
Sent: 02 May 2013 08:30
To: Nkese Mc Shine
Cc: ncl-talk@ucar.edu
Subject: Re: Correlation Question

Ho Nkese

If you have an array: x(lat,lon,time)

You can use the named dimensions to reorder

xNew = x(time|:,lat|:,lon|:)
printVarSummary(xNew)

Then you can compute the pattern correaltion(s)

Good Luck

On 5/2/13 3:22 AM, Nkese Mc Shine wrote:
> Will,
>
> Thank you for the explanation and suggestion however I do not think that will work as pattern_cor the rightmost dimension must be lon, and my monthly data which is 1 value is in time.
>
> Thank you.
> Nkese.
> ________________________________
> From: Will Hobbs [Will.Hobbs@utas.edu.au]
> Sent: 30 April 2013 19:37
> To: Nkese Mc Shine; ncl-talk@ucar.edu
> Subject: Re: Correlation Question
>
> Nkese
>
>> I would like to make a month to month correlation. I would like to correlate 1 month of sst(lat,lon,time) with 1 month of precipitation which actually is 1 value. Is it possible?
>
> No, you can't correlate a single value (in this case a month). This is nothing to do with NCL's capability, but fundamental to what a correlation is, i.e. a comparison of two variances. A single realisation (in your case a month) does not have a variance.
>
> What you can do (in case I misunderstood your question) is correlate the spatial pattern with that of a a single month; the output would be a time series of correlations. This can be done in NCL using the function 'pattern_cor()'
>
> Will
>
> From: Nkese Mc Shine <Nkese.McShine@sta.uwi.edu<mailto:Nkese.McShine@sta.uwi.edu>>
> Date: Wednesday, 1 May 2013 12:11 AM
> To: "ncl-talk@ucar.edu<mailto:ncl-talk@ucar.edu>" <ncl-talk@ucar.edu<mailto:ncl-talk@ucar.edu>>
> Subject: Correlation Question
>
> Dear All,
>
> I would like to make a month to month correlation. I would like to correlate 1 month of sst(lat,lon,time) with 1 month of precipitation which actually is 1 value. Is it possible? Attached is my script and below is the output. Please let me know, what I can do if it is possible.
>
> Variable: sst_anom
> Type: float
> Total Size: 105408000 bytes
> 26352000 values
> Number of Dimensions: 3
> Dimensions and sizes: [lat | 100] x [lon | 360] x [time | 732]
> Coordinates:
> lat: [49.5..-49.5]
> lon: [-179.5..179.5]
> time: [194601..200612]
> Number Of Attributes: 12
> anomaly_op_ncl : Annual Cycle Removed:function rmMonAnnCycLLT:contributed.ncl
> description : HadISST 1.1 monthly average sea surface temperature
> actual_range : ( -1.8, 34.76296 )
> missing_value : -1e+30
> _FillValue : -1e+30
> scale_factor : 1
> cell_methods : time: lat: lon: mean
> units : degC
> standard_name : sea_surface_temperature
> long_name : Monthly 1 degree resolution SST
> reference : function rmMonAnnCycLLT in contrib.ncl
> (0)
> (0) Monthly 1 degree resolution SST: min=-8.70077 max=6.98223
>
> Variable: sst_anom_jan
> Type: float
> Total Size: 144000 bytes
> 36000 values
> Number of Dimensions: 3
> Dimensions and sizes: [lat | 100] x [lon | 360] x [time | 1]
> Coordinates:
> lat: [49.5..-49.5]
> lon: [-179.5..179.5]
> time: [199301..199301]
> Number Of Attributes: 12
> reference : function rmMonAnnCycLLT in contrib.ncl
> long_name : Monthly 1 degree resolution SST
> standard_name : sea_surface_temperature
> units : degC
> cell_methods : time: lat: lon: mean
> scale_factor : 1
> _FillValue : -1e+30
> missing_value : -1e+30
> actual_range : ( -1.8, 34.76296 )
> description : HadISST 1.1 monthly average sea surface temperature
> anomaly_op_ncl : Annual Cycle Removed:function rmMonAnnCycLLT:contributed.ncl
> (0)
> (0) Monthly 1 degree resolution SST: min=-2.4631 max=2.59599
>
> Variable: precipanom_data_ts
> Type: float
> Total Size: 2928 bytes
> 732 values
> Number of Dimensions: 1
> Dimensions and sizes: [time | 732]
> Coordinates:
> time: [194601..200612]
> Number Of Attributes: 1
> _FillValue : 9.96921e+36
> (0)
> (0) min=-1.73324 max=3.01711
>
> Variable: precipJJA1993
> Type: float
> Total Size: 4 bytes
> 1 values
> Number of Dimensions: 1
> Dimensions and sizes: [time | 1]
> Coordinates:
> time: [199307..199307]
> Number Of Attributes: 2
> _FillValue : 9.96921e+36
> NMO : 6
> (0)
> (0) min=0.267831 max=0.267831
> warning:escorc: Non-fatal conditions encountered in series or xstd equals zero.
> Possibly, all values of a series are constant.
>
> warning:escorc: Most likely, one or more series consisted of all constant values
>
> Variable: corr
> Type: float
> Total Size: 144000 bytes
> 36000 values
> Number of Dimensions: 2
> Dimensions and sizes: [100] x [360]
> Coordinates:
> Number Of Attributes: 1
> _FillValue : -1e+30
> (0)
> (0) min=-1e+30 max=-1e+30
>
> Regards,
> Nkese.
>
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Received on Thu May 2 08:48:45 2013

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