r - 形状文件的质心

我已经通过使用unionSpatialPolygons融合了多边形来创建了shapefile，如何找到已经创建的新多边形的坐标？

最佳答案

这是两个选项，具体取决于您要计算的质心类型。我从一些维基百科页面上获取了这些算法。

# polyx and polyy are the x and y coordinates of the polygon vertices
# notice had to negate these calcs in final line...
 require(pracma,quietly=TRUE)

pchit <- polyarea(polyx,polyy)
    centx <- centy <- 0
    for (kk in 1:(length(polyx)-1) ) {
        centx <- centx + (polyx[kk]+polyx[kk+1]) * (polyx[kk]*polyy[kk+1]-polyx[kk+1]*polyy[kk])
        centy <- centy + (polyy[kk]+polyy[kk+1]) * (polyx[kk]*polyy[kk+1]-polyx[kk+1]*polyy[kk])
    }
    centx <- -1/pchit/6 * centx
    centy <- -1/pchit/6 * centy
    #  These next two are for vertex centroid, rather than polygon centroid
    # centx <- mean(polyx)
    # centy <- mean(polyy)

关于r - 形状文件的质心，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/20327244/