From: Sara Maxwell <smaxwell_at_ucsc.edu>

Date: Thu, 21 Apr 2011 18:33:22 -0700

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Fri 22 Apr 2011 - 02:33:05 GMT

Date: Thu, 21 Apr 2011 18:33:22 -0700

Hi David et al,

Thanks for your help. I spent the afternoon and thought that would
work but then I realized it was giving a different answer.

Sara M. Maxwell, Ph.D.

On Apr 21, 2011, at 1:26 PM, David Winsemius wrote:

*>
*

> On Apr 21, 2011, at 3:23 PM, Sara Maxwell wrote:

*>
**>> I am working with a raster and want to take values assigned to each
**>> cell and sort them from largest to smallest, then cummulatively sum
**>> them together (in order from largest to smallest). I'll then be
**>> coding the individual cells such that the top 10% of the largest
**>> cell values can be visualize with one color, the next 10% with
**>> another and so on.
**>>
**>> I have tried a number of schemes but am having trouble figuring out
**>> how to chose the maximum value, code it and re-search the raster
**>> for the next highest value without replacement. I am assuming this
**>> requires a loop, unless there is a function that will do this
**>> automatically.
**>
**> ?quantile
**>
**>>
**>> Here is a sample dataset:
**>>
**>> library(raster)
**>> r <- raster(ncol=10, nrow=10)
**>> values(r) <- runif(ncell(r))
**>
**>
**> > quantile(values(r), prob=seq(0,1,by=0.1))
**> 0% 10% 20% 30% 40%
**> 0.004888148 0.106378528 0.217009097 0.307201289 0.364990984
**> 50% 60% 70% 80% 90%
**> 0.512523817 0.593382875 0.667916094 0.722919876 0.835839832
**> 100%
**> 0.996683575
**>
**> You will also need findInterval()
**>
**> If you want to create a factor that will assign your colors. perhaps
**> this could be used to index a suitable color vector:
**>
**> fac <- findInterval(values(r), quantile(values(r),
**> prob=seq(0,1,by=0.1)) )
**> > fac
**> [1] 6 10 1 10 7 7 8 10 2 9 9 1 6 2 9 1 9 4 2 2
**> [21] 3 4 8 9 7 1 9 2 10 5 4 9 8 1 8 10 1 11 3 5
**> [41] 5 6 6 5 6 7 4 7 5 3 8 6 3 4 10 4 7 7 8 9
**> [61] 10 4 1 8 8 8 3 7 5 1 9 5 2 7 2 10 3 8 4 9
**> [81] 6 6 2 6 10 5 5 4 3 6 2 2 1 3 3 3 4 7 1 5
**>
**> David Winsemius, MD
**> West Hartford, CT
**>
*

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