Apply() function on 3rd dimension of SpatialGridDataFrame

Hello,

 

I have a 3D array with an attribute converted to SpatiaGridDataFrame named
?clip? :

 

summary(clip)

Object of class SpatialGridDataFrame

Coordinates:

         min       max

s1 828104.00 828134.00

s2 101839.00 101869.00

s3    324.09    373.09

Is projected: TRUE

proj4string :

[+init=epsg:27561 +proj=lcc +lat_1=49.50000000000001
+lat_0=49.50000000000001 +lon_0=0

+k_0=0.999877341 +x_0=600000 +y_0=200000 +a=6378249.2 +b=6356515

+towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs]

Grid attributes:

   cellcentre.offset cellsize cells.dim

s1         828104.50        1        30

s2         101839.50        1        30

s3            324.59        1        49

Data attributes:

    Min.  1st Qu.   Median     Mean  3rd Qu.     Max.     NA's 

   0.000    0.000    0.000    0.002    0.000    0.806 9506.000

 

The apply() function does not work on the 3rd dimension of the
SpatiaGridDataFrame :

 

D.tls.z.mean <- apply(clip, 3, mean, na.rm=T)

 

=> I get an error message (sorry it's in French) :

"Erreur dans if (d2 == 0L) { : valeur manquante l? o? TRUE / FALSE est
requis"

 

I tried with z coordinate instead :

z <- coordinates(clip)[,3]

D.tls.z.mean <- apply(clip, z, mean, na.rm=T)

 

The only solution I found is to convert back to standard non spatial 3D
array.

 

Cheers,

 

Nathalie MORIN

Doctorante en t?l?d?tection foresti?re (Ph.D student in remote sensing
applied to forestry)

Centre d?application et de recherches en t?l?d?tection (CARTEL)

D?partement de G?omatique Appliqu?e

Sherbrooke (QC) CANADA J1K 2R1

T?l. : + 1 (819)  821-8000 #62962

e-mail :  <mailto:Nathalie.M.Morin at Usherbrooke.ca>
Nathalie.M.Morin at Usherbrooke.ca

 <http://www.usherbrooke.ca/> Universit? de Sherbrooke

 

Dear Edzer,

1) as.array()
/"Would an as.array(clip) method for
SpatialGridDataFrame help you further?"/

Yes, as I mentionned in my initial post :
/"The only solution I found is to convert back to standard non spatial 3D
array."/
(in order to make the apply() function work on my 3rd dimension or z layer)

I still encounter a problem though :

D.tls.SPGDF <- SpatialGridDataFrame(D.tls.SPG, D.tls.DF)

buffer <- readOGR("donnees/limites", layer="bure_106_buffer")
buffer.proj <- spTransform(buffer, CRS("+init=epsg:27561"))
g <- geometry(buffer.proj)

fullgrid(D.tls.SPGDF) = FALSE
clip <- D.tls.SPGDF[g,,drop=TRUE] 
fullgrid(clip) = TRUE

A <- as.array(clip$d)
DA <- apply(A, 3, mean, na.rm=T)
=> gives an error message related to a missing value where TRUE / FALSE is
required
"Erreur dans if (d2 == 0L) { : valeur manquante l? o? TRUE / FALSE est
requis"

I suspect this could be related to the fullgrid() ?

2) /Or is it something else you need,
e.g. clipping a SpatialGridDataFrame with more than 2 dimensions? /

This is another story ! For the moment, I do not need a convex hull because
I do not want to truncate the height information on the z axis. But this is
an interesting question. I should probably open a separate post for that.










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