[apologies for taking the liberty to re-sort previous posts] Milton Cezar Ribeiro:
> > I have a set of 7 raster maps.
> > I am able to calculate several stats with these mapas using r.series.
> > Now I need to calculate the mean of the tree highest values of my 7 maps.
> > Any idea of how can I do that?
José Miguel Barrios wrote:
> A possible approach could be, for example, to do the following with each
> map:
> r.stats -1 input=map1 outputÎllvaluesmap1
> It will create a file containing the cell values for each map. Then you
> can read this file into R and average the three highest values. Something
> like:
> values.map1<-read.table("cellvaluesmap1")
> threehighest<-values.map1$V1[order(values.map1,decreasingúLSE)][1:3]
> mean3highest<-mean(threehighest)
If in Linux, there are several ways to do this. One (very) nice approach as
shown in <http://stackoverflow.com/a/3096575/1172302>, could be:
# get the numbers
r.stats -1 input=map1 output=Values1
# sort and keep first 3
sort -rn Values1 | head -3 > Values1.sorted
# sum and divide by 3
echo "( $( paste -sd+ Values1.sorted ) ) / 3" | bc
# or a one-liner!
sort -rn numbers | head -3 | echo "( $( paste -sd+ ) ) / 3" | bc
Other options would be "awk" or "python". Also, note that r.stats has also
the "-x" and "-g" flags. You could grab them as well and, if doing the math
"externally", know where to place the results each time?
However, it seems like a very "resources" hungry approach, if your maps are
many and large. There must be a "smart"(er) way to do this directly using
r.mapcalc...
Best, Nikos
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