Vaclav Petras wrote: > what is the right replacement for r.sum? The NewFeatures [1] (1) page says: > > r.sum: merged into G7:r.statistics, G7:r.statistics2, G7:r.statistics3 > > However, it seems to me that r.univar is the replacement. But on the other > hand, r.univar always computes all statistics, so there is certainly some > overhead and also reading requires some additional time. This might be > significant if you use r.univar in loop, for example with temporal data.
r.univar is the replacement for r.sum. r.statistics and r.stats.zonal (which is the new name for r.statistics2) create a new map which is a copy of the base map but with the categories replaced by the aggregate value computed over the corresponding cells from the cover map. You could get a similar result to r.univar by using r.stats.zonal with the -r switch and a base map where all cells contain the same category value (created using e.g. r.mapcalc "basemap = 1"), then extracting the value from the reclass table. But that's inefficient, due to the additional I/O overhead (even for a 1x1 cell map, it will still perform the decoding and rescaling for each row). The calculation of additional aggregates by r.univar shouldn't have a noticeable effect upon performance so long as -e isn't used. The calculations are trivial compared to the I/O overhead. -- Glynn Clements <[email protected]> _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
