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Crop / clip a SpatialPixels* object

4 messages · Mark Payne, Johannes Signer, Lionel +1 more

Original
Mark Payne
# 
Hi,

This should be simple, but I simply can't find an "elegant" solution.

I have a SpatialPixelsDataFrame that I would like to clip (crop) to a
smaller object. For example,
min    max
x 178440 181560
y 329600 333760
I would like to constrain m, to all y > 331000 and x >180000. What is
the most efficient way to do this (and have the other functionality
e.g bbox and plotting) reflect this reduced data set.

Mark
Lionel
# 
In this example it is pretty straightforward using the subset function:

m1<-subset(m,y>331000 & x>180000)
bbox(m1)

See this link for another way to do this using rgeos:
http://stackoverflow.com/questions/13982773/crop-for-spatialpolygonsdataframe

Cheers,
Lionel
On 22/06/2013 15:24, Mark Payne wrote:
Edzer Pebesma
# 
The way you specified the SpatialPixelsDataFrame preserves x and y as
attributes, which is good for this purpose; when e.g. built with

gridded(meuse.grid) = ~x+y

they are removed as attributes, and meuse.grid$x no longer gives the x
coordinate (we might correct this at some stage).

As an alternative to subset you can use subsetting by [, as in:

plot(m[m$x > 180000 & m$y > 332000,])

Alternatively, if you have some spatial object x denoting a clipping
region, e.g. created by

x = as(m[m$x > 180000 & m$y > 332000,], "SpatialPolygons")

you can use

m[x,]

to do the clipping. This latter statement is short for

m[!is.na(over(x,geometry(m))),]
On 06/22/2013 04:06 PM, Lionel Hertzog wrote: