Re: [R-sig-Geo] FW: Interpolcation option: IDW or OK?

2009-02-09 Thread Edzer Pebesma
Yong Li wrote: Hi Edzer, I would say the spatial structure is regarded not significant when c0/c0+c1 is very much greater than 75%. In my case I used even distance intervals and calculated c0/c0+c1 for log(OLSENP) greater than 85%. I knew this index sometimes is very fragile, very much

[R-sig-Geo] error rgdal library if used from within Grass plugin (Windows)

2009-02-09 Thread Agustin Lobo
Hi! The following error only occurs if the R (2.7.2) session is started from a GRASS shell opened through the QGIS GRASS plugin in windows. The error does not occur If R is started form its own icon or by double click in the .RData object, but then the spgrass6 package would not find the GRASS

Re: [R-sig-Geo] error rgdal library if used from within Grass plugin (Windows)

2009-02-09 Thread Roger Bivand
On Mon, 9 Feb 2009, Agustin Lobo wrote: Hi! The following error only occurs if the R (2.7.2) session is started from a GRASS shell opened through the QGIS GRASS plugin in windows. The error does not occur If R is started form its own icon or by double click in the .RData object, but then the

Re: [R-sig-Geo] FW: Interpolcation option: IDW or OK?

2009-02-09 Thread Tomislav Hengl
Dear Yong Li, I hope you will not mind me joining this interesting discussion. If there is no evident spatial auto-correlation structure (pure nugget effect), IDW/OK are as good as randomly drawing a value from the global (normal) distribution. You can even test this using cross-validation!

[R-sig-Geo] Calculating descriptive stats from many maps

2009-02-09 Thread Rainer M Krug
Hi I have 25000 maps, generated by simulation predictions, covering the same area, and would like to calculate some descriptive stats, like mean, standard deviation, median, quartiles of all cells, to create a variability map. Is there an easy way of doing this in R? Thanks, Rainer -- Rainer

Re: [R-sig-Geo] Calculating descriptive stats from many maps

2009-02-09 Thread Tomislav Hengl
Dear Rainer, This is of course possible in R, and can be done in several ways: 1) for example, you can derive the average value using the rowSums function: maps$Nsum - rowSums(m...@data, na.rm=T, dims=1) maps$avg - maps$Nsum/(length(names(meuse.g...@data))-1) You could also loop the sd,

Re: [R-sig-Geo] Calculating descriptive stats from many maps

2009-02-09 Thread Roger Bivand
On Mon, 9 Feb 2009, Tomislav Hengl wrote: Dear Rainer, This is of course possible in R, and can be done in several ways: 1) for example, you can derive the average value using the rowSums function: maps$Nsum - rowSums(m...@data, na.rm=T, dims=1) maps$avg -

[R-sig-Geo] Interpolcation option: IDW or OK?

2009-02-09 Thread Yong Li
Many thanks for the message, Edzer. -Original Message- From: Edzer Pebesma [mailto:edzer.pebe...@uni-muenster.de] Sent: Monday, 9 February 2009 7:08 PM To: Yong Li Cc: r-sig-geo@stat.math.ethz.ch Subject: Re: FW: [R-sig-Geo] Interpolcation option: IDW or OK? Yong Li wrote: Hi Edzer,

Re: [R-sig-Geo] Calculating descriptive stats from many maps

2009-02-09 Thread Robert Hijmans
Dear Rainer, This is how can you can do it with the raster package # install.packages(raster, repos=http://R-Forge.R-project.org;) require(raster) # Try it for a few files first.. n - 10 # create a list (or vector) of file names, e.g. : fn - list() for (i in 1:n) { fn[i] - paste('myfile', i,