Mark, Thanks for that clear report. This unexpected order of the layers returned by stackApply is due to a bug which only reveals itself if "unique(indices)" is not sorted from 1 to n. This has been fixed in version 2.5-1 (you can now also use a factor variable, but that should not matter). This version should be available here soon: https://r-forge.r-project.org/R/?group_id=294
Robert On Fri, Dec 11, 2015 at 12:03 AM, Mark R Payne <markpayneatw...@gmail.com> wrote: > Hi, > > [reposted from r-help] > > I am trying to use stackApply() to perform averages over subsets of a > brick. However, I am struggling with the indices argument, and how it > should be interpreted. Here is a simple working example illustrating my > problem: > > r <- raster() > r[] <- 1 > > inp <- brick(r,r,r,r,r,r)*(1:6) > res <- stackApply(inp,c(2,2,3,3,1,1),mean) > > Now if we look at the values of each object: > >> inp > names : layer.1, layer.2, layer.3, layer.4, layer.5, layer.6 > min values : 1, 2, 3, 4, 5, 6 > max values : 1, 2, 3, 4, 5, 6 > >> res > names : layer.1, layer.2, layer.3 > min values : 3.5, 5.5, 1.5 > max values : 3.5, 5.5, 1.5 > > Now, the problem is that the names and order of the layers in "res" don't > line up with the indices that I provided. You can do the maths in your head > - e.g. the first two layers of "inp" have values of 1 and 2, so their mean > should be 1.5 - however, this is ending up as layer 3 in "res". > > So how should the indices argument be interpreted in this context? > > Suggestion: A more intuitive format for the "indices" argument in > stackApply might be as a factor - this way the order is implict and > stackApply ends up working similar to split() or tapply()... > > Best wishes, > > Mark > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo