Summary of multiple rasters

Dear Johannes,

Looks like you are in the field of error propagation [http://spatial-accuracy.org/workshopSUP]. 

Both mean and median are valid statistical parameters to describe the central tendencies. What is often more interesting is the propagated uncertainty in the final estimates. I assume that your output is a binomial variable? In our 
HESS paper [http://www.hydrol-earth-syst-sci-discuss.net/7/767/2010/hessd-7-767-2010.html], we use the Information entropy index to quantify the uncertainty of the model (we deal with a binary/Bernoulli variable). The code and the dataset can be obtained from: [http://geomorphometry.org/content/uncertainty-stream-networks-derived-elevation-data]

A number of (Gaussian) grid statistics parameters can be derived using SAGA GIS:

library(RSAGA)
rsaga.get.usage(lib="geostatistics_grid", module=5)

SAGA CMD 2.0.3
library path:   C:/PROGRA~1/R/R-210~1.1/library/RSAGA/saga_vc/modules
library name:   geostatistics_grid
module name :   Statistics for Grids
Usage: 5 -GRIDS <str> [-MEAN <str>] [-MIN <str>] [-MAX <str>] [-VAR <str>] [-STDDEV <str>] [-STDDEVLO <str>] [-STDDEVHI <str>]
  -GRIDS:<str>          Grids
        Grid list (input)
  -MEAN:<str>           Arithmetic Mean
        Grid (optional output)
  -MIN:<str>            Minimum
        Grid (optional output)
  -MAX:<str>            Maximum
        Grid (optional output)
  -VAR:<str>            Variance
        Grid (optional output)
  -STDDEV:<str>         Standard Deviation
        Grid (optional output)
  -STDDEVLO:<str>       Mean less Standard Deviation
        Grid (optional output)
  -STDDEVHI:<str>       Mean plus Standard Deviation



HTH,

T. Hengl

-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-
bounces at stat.math.ethz.ch] On Behalf Of Johannes Signer
Sent: Sunday, May 02, 2010 5:30 PM
To: r-sig-geo at stat.math.ethz.ch
Subject: [R-sig-Geo] Summary of multiple rasters

Dear List,

my problem is as follows:

I have a model that predicts me the distribution  of a species in the
landscape. I run that model several times and now I am not sure which
summary statistic to use (mean, median). Is there an index to get an idea of
how the prediction in each cell are distributed?

Any are greatly appreciated,

Thanks
Johannes

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