[R-sig-Geo] Overlay-ing two grids

[Renaud Lancelot]

Thank you for the different solutions which all work fine.

Kind regards,

Renaud

2009/12/22, Robert J. Hijmans <r.hijmans at gmail.com>:
> Renaud,
> Here another way:
>
> library(raster)
> r <- raster(sgdf1, 1)
> ra <- aggregate(r, 10, mean)
> sgdf3 <- as(ra, 'SpatialGridDataFrame')
>
>> values(ra)
>   [1] 0.43 0.45 0.57 0.50 0.49 0.47 0.58 0.50 0.61 0.49 0.49 0.53 0.54
> 0.51 0.53 0.42 0.48 0.51 0.54 0.53 0.50
>  [22] 0.52 0.39 0.52 0.52 0.62 0.53 0.48 0.52 0.48 0.52 0.45 0.50 0.48
> 0.43 0.47 0.52 0.49 0.43 0.59 0.54 0.52
>  [43] 0.53 0.53 0.48 0.57 0.46 0.54 0.49 0.48 0.47 0.48 0.47 0.50 0.48
> 0.49 0.47 0.45 0.50 0.52 0.54 0.46 0.49
>  [64] 0.52 0.54 0.50 0.46 0.43 0.49 0.46 0.55 0.52 0.52 0.47 0.41 0.51
> 0.56 0.40 0.56 0.50 0.47 0.48 0.55 0.44
>  [85] 0.57 0.44 0.51 0.49 0.50 0.49 0.56 0.54 0.46 0.50 0.52 0.49 0.52
> 0.42 0.57 0.54
>>
>
> Robert
>
> On Tue, Dec 22, 2009 at 1:36 AM, Renaud Lancelot
> <renaud.lancelot at cirad.fr> wrote:
>> Dear all,
>>
>> I have two "nested" grids (SpatialGridDataFrame) looking like this:
>>
>> prj <- "+proj=utm +zone=28 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
>> gt1 <- GridTopology(c(5, 5), c(10, 10), c(100, 100))
>> gt2 <- GridTopology(c(50, 50), c(100, 100), c(10, 10))
>> band1 <- sample(c(0, 1), replace = TRUE, size = 10000)
>> sgdf1 <- SpatialGridDataFrame(gt1, data.frame(band1), CRS(prj))
>> sgdf2 <- SpatialGridDataFrame(gt2, data.frame(band1=rep(0, 100)),
>> CRS(prj))
>> ## Graphic display
>> spplot(sgdf1, scales = list(draw = TRUE),
>>       panel = function(...){
>>           panel.gridplot(...)
>>           sp.grid(sgdf2, col = 0)
>>           })
>>
>> I want to compute the mean (and other statistics) of sgdf1 at data$band1
>> according to the cells defined in sgdf2. How can I do that ? I tried to
>> use
>> overlay, without success:
>>
>>> sgdf3 <- overlay(sgdf1, sgdf2, fn = mean)
>>> sgdf3 at data$band1
>>  [1] 1 0 0 0 0 0 1 1 1 0 0 1 0 0 0 0 0 1 1 0 1 0 1 1 0 1 0 0 0 0
>>  [31] 0 0 1 0 1 1 1 0 0 0 0 0 0 1 0 1 1 0 0 0 1 0 1 0 1 0 1 1 0 0
>>  [61] 1 1 0 1 1 1 1 0 0 0 1 1 0 0 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0
>>  [91] 1 0 1 1 1 0 1 0 1 0
>>
>> All the best,
>>
>> Renaud
>>
>>
>>
>> --
>> Renaud Lancelot
>> EDEN Project, coordinator
>> http://www.eden-fp6project.net/
>> << EDEN International Conference, Montpellier,  10-12 May 2010 >>
>> <<   http://international-conference2010.eden-fp6project.net/  >>
>>
>> UMR CIRAD-INRA "Contrôle des maladies animales exotiques et émergentes"
>> Joint research unit "Control of emerging and exotic animal diseases"
>>
>> CIRAD, Campus International de Baillarguet TA A-DIR / B
>> F34398 Montpellier
>> http://www.cirad.fr  http://bluetongue.cirad.fr/
>>
>> Tel.  +33 4 67 59 37 17  -  Fax  +33 4 67 59 37 95
>> Secr. +33 4 67 59 37 37  - Cell. +33 6 77 52 08 69
>>
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>
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-- 
Renaud Lancelot
EDEN Project, coordinator
http://www.eden-fp6project.net/
<< EDEN International Conference, Montpellier,  10-12 May 2010 >>
<<   http://international-conference2010.eden-fp6project.net/  >>

UMR CIRAD-INRA "Contrôle des maladies animales exotiques et émergentes"
Joint research unit "Control of emerging and exotic animal diseases"

CIRAD, Campus International de Baillarguet TA A-DIR / B
F34398 Montpellier
http://www.cirad.fr  http://bluetongue.cirad.fr/

Tel.  +33 4 67 59 37 17  -  Fax  +33 4 67 59 37 95
Secr. +33 4 67 59 37 37  - Cell. +33 6 77 52 08 69