[R-sig-Geo] Create a mask for multiple polygons in spatstat package

[ASANTOS]

Dear Members,

          I try to create a mask for multiple polygons in spatstat with 
union.owin that is much quicker than the "mask" type, but I have some 
problems that involves list objects and I ask if is posible to use 
union.owin with matrix object? In my example:

require(spatstat)
require(sp)
require(gpclib)


# Two polygons 
coordinates------------------------------------------------------

#Polygon 1
x.coords1<-c(371299.9,    371266.4,    371205.6,    371111.8, 
371047.6,    371018.2,    371014.0,
               371009.3,    370983.1,    370919.7,    370853.6, 
370785.6,    370748.8,    370711.8,
               370687.8,    370696.4,    370785.9,    370885.5, 
371035.8,    371148.1,    371205.2,
               371231.7,    371236.5,    371240.3,    371285.8, 
371326.5,    371397.2,    371417.1,
               371432.9,    371445.0,    371455.7,    371466.4, 
371476.6,    371502.6,    371536.0,
               371550.0,    371546.8,    371528.3,    371470.0, 
371393.3,    371299.9,    371299.9)

y.coords1<-c(8246589,    8246560,    8246508,    8246428, 8246373,    
8246349,    8246348,
              8246352,    8246385,    8246465,    8246551, 8246638,    
8246685,    8246732,
              8246764,    8246771,    8246846,    8246932, 8247062,    
8247160,    8247209,
              8247230,    8247224,    8247221,    8247160, 8247107,    
8247016,    8246991,
              8246967,    8246939,    8246914,    8246892, 8246875,    
8246846,    8246821,
              8246809,    8246802,    8246785,    8246735, 8246669,    
8246589,    8246589)

#Polygon 2

x.coords2<-c(368382.9,    368399.4,    368394.1,    368464.7, 
368652.2,    368683.7,    368699.7,
              368714.9,    368714.9,    368714.9,    368860.9, 
368932.1,    368994.8,    368994.8,
              369015.7,    369014.5,    369014.5,    369026.8, 
369045.2,    369020.0,    368952.9,
              368951.4,    368952.9,    368951.4,    368936.8, 
368923.4,    368804.1,    368676.0,
              368178.1,    368182.4,    368202.2,    368216.2, 
368233.4,    368251.3,    368270.3,
              368281.7,    368300.6,    368323.8,    368344.8, 
368364.6,    368374.2,    368382.9)



y.coords2<-c(8249120,    8249150,    8249153,    8249244, 8249173,    
8249167,    8249154,
                 8249145,    8249145,    8249145,    8249048, 
8249026,    8249003,    8249003,
              8248993,    8248991,    8248991,    8248984, 8248970,    
8248889,    8248833,
              8248829,    8248833,    8248829,    8248790, 8248765,    
8248626,    8248526,
              8248774,    8248780,    8248815,    8248843, 8248871,    
8248903,    8248934,
              8248952,    8248978,    8249013,    8249049, 8249086,    
8249103,    8249120)


# Mask creation 
---------------------------------------------------------------

mult.poly<-cbind(c(x.coords1,x.coords2),c(y.coords1,y.coords2))

w <- do.call(union.owin,mult.poly)

plot(w)

#-------------------------------------------------------------------------------


Thanks,


-- 
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Alexandre dos Santos
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