sp R包SpatialPolygons-Class plot transparent

我想用透明填充顏色來繪製類SpatialPolygons的對象。從SpatialPolygons-Class的幫助頁稍微更改示例：sp R包SpatialPolygons-Class plot transparent

# simple example, from vignette("sp"): 
Sr1 = Polygon(cbind(c(2,4,4,1,2),c(2,3,5,4,2))) 
Sr2 = Polygon(cbind(c(5,4,2,5),c(2,3,2,2))) 
Sr3 = Polygon(cbind(c(4,4,5,10,4),c(5,3,2,5,5))) 
Sr4 = Polygon(cbind(c(5,6,6,5,5),c(4,4,3,3,4)), hole = TRUE) 

Srs1 = Polygons(list(Sr1), "s1") 
Srs2 = Polygons(list(Sr2), "s2") 
Srs3 = Polygons(list(Sr3, Sr4), "s3/4") 
SpP = SpatialPolygons(list(Srs1,Srs2,Srs3), 1:3) 
plot(1,1,type="n",ylim=c(0,10),xlim=c(0,10),xlab="",ylab="",yaxt="n",xaxt="n") 
plot(SpP, col = paste0(c("#FF0000","#00FF00","#0000FF"),"55"), pbg="white",add=TRUE)

工作正常。但是，如果我要放大，情節SpatialPolygons級方法無法處理的透明瞭：

plot(1,1,type="n",ylim=c(0,7),xlim=c(0,7),xlab="",ylab="",yaxt="n",xaxt="n") 
plot(SpP, col = paste0(c("#FF0000","#00FF00","#0000FF"),"55"), pbg="white",add=TRUE)

有沒有辦法得到這個工作？（如果可能，我想保留傳統的plot函數）

來源

2016-04-21 Chris

解決此問題的一種方法是剪切多邊形。

c1 <- Polygon(cbind(c(0,7,7,0, 0),c(0,0,7,7,0))) 
c2 <- Polygons(list(c1), "sclip") 
Pclip <- SpatialPolygons(list(c2)) 
library(rgeos) 
SpPclip <- gIntersection(SpP, Pclip, byid = T) 
plot(SpPclip, col = paste0(c("#FF0000","#00FF00","#0000FF"),"55"), pbg="white", 
    ylim = c(-1,10), xlim = c(-1,10)) 
plot(Pclip, add = T)

輸出看起來是這樣的：

來源

2016-04-21 15:56:12 loki

謝謝！這解決了它。注意：爲了得到與我的例子相同的圖形，必須擴展'Pclip'多邊形默認的繪圖區域的4％擴展：'c1 < - Polygon（cbind（c（-0.28,7.28,7.28， - 0.28，-0.28），c（-0.28，-0.28,7.28,7.28，-0.28）））'並且沒有限制的繪圖。 – Chris

sp R包SpatialPolygons-Class plot transparent

回答

相關問題