[R-sig-Geo] Clip SpatialGridDataFrame with SpatialPolygons

[Nathalie Morin]

Hello!

 

I have already searched the Forum’s archives and sp documentation, but the
answer is still unclear to this basic question : how can you clip a
SpatialGridDataFrame with a SpatialPolygons and return a new clipped
SpatialGridDataFrame (not a vector !).

 

Here is my data as an example :

 

> summary(D.tls.SPGDF)

Object of class SpatialGridDataFrame

Coordinates:

            min        max

[1,] 828049.000 828191.000

[2,] 101770.000 101915.000

[3,]    321.632    480.632

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

1        828049.500        1       142

2        101770.500        1       145

3           322.132        1       159

Data attributes:

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

   0.000    0.000    0.000    0.000    0.000    0.969 6895.000 

 

> summary(g)
Object of class SpatialPolygons
Coordinates:
       min      max
x 828103.9 828133.9
y 101839.3 101869.3
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]

 

If I do :

> o <- overlay(D.tls.SPGDF, g)

R returns a vector 

 

Which is the function that returns the initial object i.e.
SpatialGridDataFrame ?

 

Nathalie

 

Nathalie MORIN

Doctorante en télédétection forestière (Ph.D student in remote sensing
applied to forestry)

Centre d’application et de recherches en télédétection (CARTEL)

Département de Géomatique Appliquée

Sherbrooke (QC) CANADA J1K 2R1

Tél. : + 1 (819)  821-8000 #62962

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

 <http://www.usherbrooke.ca/> Université de Sherbrooke

 

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