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

[gibies george]

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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