[ncl-talk] Running correlation giving same value for all the different years

[Ipshita Majhi]

Thank you will keep that in mind
Best Regards
Ipshita

On Thu, Oct 30, 2014 at 11:45 AM, gibies george <gibiesgeorge at gmail.com>
wrote:

> Question 1 and 2 meant to remind you that NCL use FORTRAN indexing. 0, 1,
> 2, 3, ......
> On Oct 30, 2014 8:38 PM, "Ipshita Majhi" <ipmajhi at alaska.edu> wrote:
>
>> Thank you . Yes! I realised that my script was not doing the running
>> correlation instead it was doing correlation for every 15 year time
>> step.Answer to the questions are as follows:-
>>
>> 1. Why 7:10 is the data starting third column ? Any way not related to
>> your question.
>>
>> I am calculating average for summer months of monsoon June, July, August
>> and September and that is the column 7:10
>>
>> JJAS_avg=dim_avg_n(JJAS,1)
>> ;print(dimsizes(JJAS_avg))
>>
>> years=air(:,1)
>>
>> 2. Years is the first column from air which has information for year
>> going from 1871 to 2012
>>
>> I am incorporating the suggestion recommended.
>>
>> Thank You
>> Best Regards
>> Ipshita
>>
>>
>>
>> On Thu, Oct 30, 2014 at 2:48 AM, gibies george <gibies at tropmet.res.in>
>> wrote:
>>
>>> I have a few comments on your script.
>>>
>>>
>>> On 30 October 2014 02:43, Ipshita Majhi <ipmajhi at alaska.edu> wrote:
>>>
>>>> Dear all,
>>>>
>>>> I want to calculate running correlation for All India Rainfall and I am
>>>> not able to use run_cor because the time dimension does not make sense for
>>>> me. I wrote a loop but I get the same value for all the period. There is no
>>>> error in the code output. I am not sure where i am going wrong. It will be
>>>> great if someone can help
>>>>
>>>>
>>>>
>>>> ;This is to get a 15 and 20 year running correlation for JJAS
>>>>
>>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/contrib/run_cor.ncl"
>>>>
>>>>
>>>> ncol = 12
>>>> nrows=133
>>>>
>>>> ;Reading in the data from 1871 to 2012
>>>>
>>>> air=readAsciiTable("~/Documents/PhD_June_2015/Data_AIR/air_1871_2012.txt",
>>>> ncol, "integer",2)
>>>>
>>>> ;Extracting Indian summer monsoon months
>>>>
>>>> JJAS=air(:,7:10)
>>>>
>>> 1. Why 7:10 is the data starting third column ? Any way not related to
>>> your question.
>>>
>>>>
>>>> JJAS_avg=dim_avg_n(JJAS,1)
>>>> ;print(dimsizes(JJAS_avg))
>>>>
>>>> years=air(:,1)
>>>>
>>> 2. Do you mean second column of data?
>>>
>>>>
>>>>
>>>> ;This is running correlation for 15 years
>>>>
>>>>   yrStrt  = 1871
>>>>   yrLast  = 2012
>>>>
>>>>   nmos    = 12
>>>>   nyrs    = yrLast-yrStrt+1
>>>>   n_15 = nyrs/15
>>>>
>>>>   running_correlation_15=new(n_15,"float")
>>>>
>>>>     do nyr=0,(15*n_15)-1,15
>>>>      nyrStrt = nyr         ; clarity
>>>>      nyrLast = nyrStrt+14
>>>>      running_correlation_15(nyr/15) = escorc(years,JJAS_avg )
>>>>
>>> 3. What is variable "years" ? is it some meaningful index ?
>>>
>>>>
>>>>   end do
>>>>
>>> 4. Any way this loop is not doing the 15 year window running correlation,
>>>
>>> Suggestions
>>> 1. You need n_15=nyrs-15 to store 15 rear running correlation output.
>>> 2. You have to specify window while passing the data to the escorc
>>> function like escorc(index(y1:y15),JJAS_avg(y1:y15))
>>>
>>> 3. Within the loop you can increment y1=y1+1 and y15=y15+1 for running
>>> correlation, or you can fix the time step increment as you wish. In the
>>> above loop you are using a 15 year time step by using do
>>> nyr=0,(15*n_15)-1,15.
>>>
>>>> print(running_correlation_15)
>>>>
>>>>
>>>>
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>>>>
>>>
>>
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