[GRASS-user] calculation of mean and standard deviation of several rasters

GRASS GRASS user
1

Hello,

I've got several maps with the same regional extend and same resolution (output of several model runs). Now I'd like to calculate the mean and the standard deviation of each cell for all the overlaying rasters.

I just found the mode/median/min/max function of the mapcalculator. Is there a mean and SD function for mapcalc or is there any other way? Or do I have to calculate it by "hand" (defining the formula in mapcalc).

If not possible I also thought about exporting all maps to a numpy array and calculating with numpy/scipy but I'd like to do it in grass due to time reasons...

/johannes
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2

Johannes wrote:

I've got several maps with the same regional extend and
same resolution (output of several model runs). Now I'd like
to calculate the mean and the standard deviation of each
cell for all the overlaying rasters.

I just found the mode/median/min/max function of the
mapcalculator. Is there a mean and SD function for mapcalc
or is there any other way? Or do I have to calculate it by
"hand" (defining the formula in mapcalc).

If not possible I also thought about exporting all maps to
a numpy array and calculating with numpy/scipy but I'd like
to do it in grass due to time reasons...

-> check out r.series

Hamish

3

Johannes Radinger wrote:

I've got several maps with the same regional extend and same
resolution (output of several model runs). Now I'd like to calculate
the mean and the standard deviation of each cell for all the
overlaying rasters.

I just found the mode/median/min/max function of the mapcalculator. Is
there a mean and SD function for mapcalc or is there any other way? Or
do I have to calculate it by "hand" (defining the formula in mapcalc).

r.mapcalc doesn't have mean, variance, etc; you need to calculate them
"by hand".

But as Hamish suggests, r.series is probably the right tool in this
particular case.

--
Glynn Clements <glynn@gclements.plus.com>