[GRASS-user] P value for slope from r.series

[Daniel Victoria]

I just read on the p-value regression ticket a comment from Markus Metz
[1]. If I understood correctly, he mentions that the chances of getting
small p-values at random is high and we should do a correction. But this
would result in non-significant p-values. He concludes that it would be
more "appropriate to make prior assumptions about slope, intercept, and
effect size, then judge the results according to these prior assumptions".

Does this means that I should not rely on the p-value obtained?

Where can I find more information about this? Some colleagues and I are in
the process of finishing a paper that uses applies a regression to annual
NDVI data and right now, we are discussing if we should (or not) consider
the p-values obtained.

Thanks and sorry if this is a bit of topic

Cheers
Daniel

[1] https://trac.osgeo.org/grass/ticket/2376#comment:3

On Mon, Oct 16, 2017 at 2:12 PM Daniel Victoria <daniel.victoria at gmail.com>
wrote:

> Replying to self and in case helps anyone.
>
> Solved it by using R and the raster package. Here is a Stackoverflow post
> about it
>
>
> https://stackoverflow.com/questions/20262999/how-to-output-regression-summarye-g-p-value-and-coeff-into-a-rasterbrick
>
> Cheers
> Daniel
>
> On Wed, Oct 11, 2017 at 10:44 AM Daniel Victoria <
> daniel.victoria at gmail.com> wrote:
>
>> OK, dumb question since I'm a bit (or very) bad at stats.
>>
>> I'm calculating the slope from a series of rasters using r.series. I see
>> that I can also get the t-value and the coefficient of determination. Is
>> there a way to get the p-value for the regression?
>>
>> I've seen that this question has been asked before (in 2012) [1] and it
>> ended with the addition of the t-value calculation in r.series. But I
>> failed to see how the p-value can be obtained.
>>
>> I also found this ticket [2], related to the p-value question.
>>
>> Thanks
>> Daniel
>>
>> [1] -
>> http://osgeo-org.1560.x6.nabble.com/Calculate-p-value-for-regression-slope-in-r-series-td5014228.html
>>
>> [2]  https://trac.osgeo.org/grass/ticket/2376
>>
>>
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