[gradsusr] trend analysis

[Maria Tereza Cavazos Perez]

Hi Andrew,

Thanks for the tips!
Cheers,

Tereza

> Hi Tereza,
>
> Admittedly I haven't used GrADS for trend significance, but here are some
> thoughts that come to mind:
>
> -ltrend.gs outputs the rmse, which can be squared to get the mse.
> -For the trend r2, you could first use the built-in function tcorr with a
> linear trend time series to get the correlation, and then square this
> correlation coefficient to get the r2.
> -I believe that the trend fit could be constructed as the slope x a linear
> trend time series, and that squaring and summing these would obtain the
> regression sum of squares (being careful about anomalies). Scaling this to
> obtain the mean regression sum of squares and dividing by the mse, you
> could get the F value.
>
> Perhaps someone with more GrADS statistics experience can offer more
> concrete suggestions.
>
> Best, Andrew
>
>> On Jan 20, 2017, at 9:21 PM, Tereza Cavazos <tcavazos at cicese.mx> wrote:
>>
>> Hi Andrew,
>>
>> Is there a way to obtain the statistical significance of the trends in
>> each point?
>>
>> Cheers,
>>
>> Tereza
>>
>> On 20/01/2017 07:59 a.m., Andrew Friedman wrote:
>>> Hi Bimal,
>>> Yes - you can use ltrend.gs to obtain gridbox trends.
>>> -Andrew
>>>
>>> On Jan 20, 2017, at 3:19 PM, Bimal Gyawali <bml.gya at gmail.com> wrote:
>>>
>>>> Hi Andrew,
>>>> Thank you very much. I think that script gives trend line. But I would
>>>> like to find the trend on every grid point. Is that possible?
>>>>
>>>> Bimal Gyawali
>>>> Graduate Research Assistant
>>>> Department of Physical and Environment Science
>>>> Natural Resources Center
>>>> Texas A&M University-Corpus Christi
>>>> Corpus Christi, TX 78412
>>>> Tel: 435-881-3603
>>>>
>>>>
>>>> On Thu, Jan 19, 2017 at 5:14 PM, Andrew Friedman <andfried at gmail.com>
>>>> wrote:
>>>> Hi Bimal,
>>>>
>>>> Check out Bin Guan’s script ltrend.gs:
>>>> http://bguan.bol.ucla.edu/bGASL.html
>>>>
>>>> Andrew
>>>>
>>>> > On Jan 19, 2017, at 11:34 PM, Bimal Gyawali <bml.gya at gmail.com>
>>>> wrote:
>>>> >
>>>> > Hi all,
>>>> > Is it possible to calculate trend analysis in spatial domain using
>>>> GrDAS? if is it possible how can it be done? Please help me. I have
>>>> monthly data (3D variable, lat, lon and time)from 2000-2016. I wanna
>>>> calculate the trend of the variable and plot the map. please help me
>>>> with this if any of you have done it before.
>>>> > THank you.
>>>> > Bimal Gyawali
>>>> >
>>>> >
>>>> >
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-- 
Tereza Cavazos
Departamento de Oceanografia Fisica
CICESE
Ensenada, Baja California, MEXICO
http://usuario.cicese.mx/~tcavazos/