Re: Statistical Significance Test in NCL

From: Soumik Basu <sbasu_at_nyahnyahspammersnyahnyah>
Date: Mon Mar 24 2014 - 15:36:32 MDT

I fixed the problem.

Thank you,

-- 
"Numbing the pain for a while will make it worse when you finally feel 
it.
  ~J.K. Rowling"
*****************************************
Soumik Basu
Graduate Student, Research Assistant
International Arctic Research Center
University of Alaska Fairbanks
Fairbanks,Alaska,USA
*****************************************
On 2014-03-24 13:08, Soumik Basu wrote:
> Thanks Dennis for the reply. I wanted to determine if two
> distributions are same but as you said the function for it isn't
> released yet. So I am now using ttest but I am getting an error :
> warning:ttest: encountered 1 cases where var1 and/or var2 were less
> than or equal to 0. Output set to missing values in these cases
> 
> I am not sure why I am getting this since I have printed out the
> variance and there is no zero or negative number.
> 
> Variable: var_p
> Type: float
> Total Size: 20 bytes
>             5 values
> Number of Dimensions: 1
> Dimensions and sizes:	[5]
> Coordinates:
> Number Of Attributes: 2
>   _FillValue :	9.96921e+36
>   variance_op_ncl :	dim_variance_n function was applied
> (0)	7.990942
> (1)	9.834744
> (2)	3.267889
> (3)	5.992806
> (4)	5.159097
> 
> Variable: var_n
> Type: float
> Total Size: 20 bytes
>             5 values
> Number of Dimensions: 1
> Dimensions and sizes:	[5]
> Coordinates:
> Number Of Attributes: 2
>   _FillValue :	9.96921e+36
>   variance_op_ncl :	dim_variance_n function was applied
> (0)	4.094823
> (1)	8.155126
> (2)	8.030828
> (3)	2.706451
> (4)	8.858122
> 
> Part of the code doing ttest is:
> 
> ;************************************************************
> ;  Get average and variance and do ttest
> ;***********************************************************
>   av_p  = dim_avg_n_Wrap(cai_p(0,:,:),1)
>   var_p = dim_variance_n_Wrap(cai_p(0,:,:),1)
>   av_n  = dim_avg_n_Wrap(cai_n(0,:,:),1)
>   var_n = dim_variance_n_Wrap(cai_n(0,:,:),1)
> 
>   print(av_p)
>   print(var_p)
>   print(av_n)
>   print(var_n)
> 
>    s1 = (/5,5,5,5,5/)
> ;   s1 = dimsizes(cai_p(0,:,:))
>    s2 = s1
>   s2 = s1
>   printVarSummary(s1)
>   siglvl = 0.05
> 
>   iflag = False
> 
>   sig = ttest(av_p,av_n,var_p,var_n,s1,s2,iflag,True)
> 
>   print(sig)
> 
> 
> Thanks,
> Soumik
> --
> "Numbing the pain for a while will make it worse when you finally feel 
> it.
>  ~J.K. Rowling"
> *****************************************
> Soumik Basu
> Graduate Student, Research Assistant
> International Arctic Research Center
> University of Alaska Fairbanks
> Fairbanks,Alaska,USA
> *****************************************
> 
> On 2014-03-24 11:16, Dennis Shea wrote:
>> On 3/24/14, 12:22 PM, Soumik Basu wrote:
>>> Hello,
>>> 
>>> Is there any function in NCL that I can use to perform a statistical
>>> significance test of PDF distribution?
>> 
>> What are you testing? What is your null hypothesis?
>> 
>> If you want to determine if two distributions are the same,
>> The in the soon-to-be-released 6.2.0 there is a
>> Kolmogorov-Smirnov two sample test. See "kolsm2_n"
>> 
>>    http://www.ncl.ucar.edu/future_release.shtml
>> 
>>> Also, is there any example showing how to mark the confidence 
>>> intervals
>>> on a PDF plot?
>> 
>> No.
>> 
>>> 
>>> Thanks,
>>> Soumik
>>> 
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Received on Mon Mar 24 15:36:45 2014

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