The univariate statistics include the number of raster cells counted, the number of raster NULL cells counted, minimum and maximum cell values, range, average, standard deviation, variance, coefficient of variation, sum, first quartile, median, third quartile, and percentile.
The module may take a long time to run if the raster region contains a large number of cells. In this case the --verbose flag may be used to track progress.
The script stops if a (prefixed) upload column is already present in the vector map attribute table, unless otherwise instructed with the -c continue flag. The column prefix will be separated from the statistic name with an underscore. For example with a prefix of "elev" the sum column will be named elev_sum.
If a DBF database is being used, note that column names are restricted by the DBF specification to 10 characters. Therefore it is advised to be economical in the use of the column prefix when using DBF as any additional characters will be chopped off.
If a MASK is present, it will be restored after the script finished. The script changes temporarily to the resolution of the given raster map.
Large amounts of system memory can be used when extended statistics (first_quartile,median,third_quartile,percentile ) are being requested with a very large region setting. If the region is too large the module should display memory allocation errors. Basic statistics can be calculated using any size input region.
g.copy vect=zipcodes_wake,myzipcodes_wake # set computational region to DEM: g.region raster=elevation -p # calculate selected DEM statistics, upload to vector map table: v.rast.stats myzipcodes_wake raster=elevation \ column_prefix=elev method=minimum,maximum,average,range,stddev,percentile \ percentile=95 # verify results: v.info -c myzipcodes_wake v.db.select myzipcodes_wake v.univar myzipcodes_wake column=elev_range type=centroid
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