Add p-value for regression slope in r series

[mastho]

The calculation of t-values has been added to r.series in r53742 (method=tvalue). It would be nice to have also the corresponding p-values for the regression as method in r.series.

Also discussed here: ​http://osgeo-org.1560.x6.nabble.com/Calculate-p-value-for-regression-slope-in-r-series-td5014228.html

[neteler]

See especially

• ​http://lists.osgeo.org/pipermail/grass-user/2012-November/066132.html
• ​http://lists.osgeo.org/pipermail/grass-user/2012-November/066141.html

[pvanbosgeo]

You can calculate the p-value using the scipy library (from ​http://stackoverflow.com/questions/17559897/python-p-value-from-t-statistic). For example, if tt is the t value

import scipy.stats as stats
import numpy as np
tt = 2.4
n = 10
pval = stats.t.sf(np.abs(tt), n-1)*2  (two-sided p-value)

Perhaps this can be used either to create a script or in r.series?

[mmetz]

Replying to pvanbosgeo:

You can calculate the p-value using the [python] scipy library

Considering that you want to calculate a p value for each single pixel, the chances that you get randomly some very small p values increase with the number of pixels. You would need to correct for that, with Bonferroni or some method that escapes the iron claw of Bonferroni. In any case, all your p values will most probably become not significant after any method of correction for multiple testing.

Therefore it is more appropriate to make prior assumptions about slope, intercept, and effect size, then judge the results according to these prior assumptions.

[martinl]

Milestone renamed

[dvictori]

You can calculate regression p-value 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

[neteler]

Ticket retargeted after milestone closed

[martinl]

All enhancement tickets should be assigned to 7.6 milestone.

[martinl]

Ticket retargeted after milestone closed

[martinl]

Ticket retargeted after milestone closed