[R-sig-Geo] Overlay and spatialgrid

[Robert J. Hijmans]

Ervan,

You can do something like

library(raster)
r <- raster(Grid2)
r <- pointsToRaster(r, xy=temp[, c('x', 'y')], values=temp[,'z'], fun=max)

plot(r)
x <- as(r, 'SpatialGridDataFrame')


On Tue, Sep 21, 2010 at 2:29 AM, Ervan Rutishauser
<ervan.rutishauser at cirad.fr> wrote:
> Dear all,
>
> I wonder if it is possible to compute a statistic (mean, max) of a
> SpatialPointsDataFrame object using a SpatialGrid.
> I tried it that way, but did not get what I wanted:
>
> # 1. Create a grid bonding the region studied
> Grid<-GridTopology(c(284600,580550),c(5,5),c(600,850))
> Grid2<-SpatialGrid(Grid)
>
> # 2. An example of my data
>> head(temp)
>         x                     y           z   R   G   B   I
> 1 284999.1 583538.0  9.76 11 10  8 65
> 2 284998.2 583537.1  6.40 10  4 11 69
> 3 284999.9 583536.1 28.70  8  8  4 75
> 4 284996.7 583535.9 12.55  4  3  0 63
> 5 284996.8 583533.8  7.64 16  6 10 75
> 6 284997.3 583532.5 26.46 11  9 10 74
>
> coord<-coordinates(matrix(c(temp$x,temp$y),ncol=2))
> Z<- data.frame(Z=temp$z,I=temp$I)
> lidar<-SpatialPointsDataFrame(coord,Z)
>
> test<-overlay(lidar, Para_gr) # I would like to compute the maximum of z in
> each cell of the grid.
>
> Thank you for any help.
> All the best,
> Ervan
> ______________________________________________________________________
> Ervan Rutishauser
> CIRAD - UMR AMAP
> PS1-Bd de la Lironde
> 34398 Montpellier cedex 5
> phone: 04.67.61.58.00
>
>
>
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