聚合 sf 空间数据帧值

Question

我想对每个多边形的值求和，表示为cod_area。

library(sf)

sf.data <- structure(list(cod_area = c(34275L, 34275L, 34347L, 34347L), 
    cod_reg = c(1664464L, 1664467L, 1665398L, 1665400L), val = c(2562.5, 
    2166.66666666667, 10288.75, 3613), geometry = structure(list(
        structure(list(structure(c(-46.5, -46.3333333, -46.3333333, 
        -46.5, -46.5, -24.3333333, -24.3333333, -24.5, -24.5, 
        -24.3333333), dim = c(5L, 2L))), class = c("XY", "POLYGON", 
        "sfg")), structure(list(structure(c(-46.5, -46.3333333, 
        -46.3333333, -46.5, -46.5, -24.3333333, -24.3333333, 
        -24.5, -24.5, -24.3333333), dim = c(5L, 2L))), class = c("XY", 
        "POLYGON", "sfg")), structure(list(structure(c(-46.6666667, 
        -46.5, -46.5, -46.6666667, -46.6666667, -24.3333333, 
        -24.3333333, -24.5, -24.5, -24.3333333), dim = c(5L, 
        2L))), class = c("XY", "POLYGON", "sfg")), structure(list(
            structure(c(-46.6666667, -46.5, -46.5, -46.6666667, 
            -46.6666667, -24.3333333, -24.3333333, -24.5, -24.5, 
            -24.3333333), dim = c(5L, 2L))), class = c("XY", 
        "POLYGON", "sfg"))), n_empty = 0L, class = c("sfc_POLYGON", 
    "sfc"), precision = 0, bbox = structure(c(xmin = -46.6666667, 
    ymin = -24.5, xmax = -46.3333333, ymax = -24.3333333), class = "bbox"), crs = structure(list(
        input = "EPSG:4674", wkt = "GEOGCRS[\"SIRGAS 2000\",\n    DATUM[\"Sistema de Referencia Geocentrico para las AmericaS 2000\",\n        ELLIPSOID[\"GRS 1980\",6378137,298.257222101,\n            LENGTHUNIT[\"metre\",1]]],\n    PRIMEM[\"Greenwich\",0,\n        ANGLEUNIT[\"degree\",0.0174532925199433]],\n    CS[ellipsoidal,2],\n        AXIS[\"geodetic latitude (Lat)\",north,\n            ORDER[1],\n            ANGLEUNIT[\"degree\",0.0174532925199433]],\n        AXIS[\"geodetic longitude (Lon)\",east,\n            ORDER[2],\n            ANGLEUNIT[\"degree\",0.0174532925199433]],\n    USAGE[\n        SCOPE[\"Horizontal component of 3D system.\"],\n        AREA[\"Latin America - Central America and South America - onshore and offshore. Brazil - onshore and offshore.\"],\n        BBOX[-59.87,-122.19,32.72,-25.28]],\n    ID[\"EPSG\",4674]]"), class = "crs"))), row.names = c(NA, 
4L), class = c("sf", "data.frame"), sf_column = "geometry", agr = structure(c(cod_area = NA_integer_, 
cod_reg = NA_integer_, val = NA_integer_), class = "factor", levels = c("constant", 
"aggregate", "identity")))

class(sf.data)
[1] "sf"         "data.frame"

我期望有两个值，cod_area 34275 为 4729.167，cod_area 34347 为 13901.75。但是...

aggregate(val~geometry,data=sf.data,FUN=sum)
Error in model.frame.default(formula = val ~ geometry, data = sf.data) : 
  invalid type (list) for variable 'geometry'


aggregate(sf.data["val"],by=list(sf.data$geometry),FUN=sum)
Error in order(y) : unimplemented type 'list' in 'orderVector1'

以及其他尝试。我以某种方式解决了这个问题

agg.val <- aggregate(val~cod_area,sf.data,FUN=sum)

merge(agg.val,unique(sf.data[,1]),by="cod_area")

有没有更直接的方法来进行计算（不使用 dplyr）？

Answer 1

无需 {dplyr} 的一种方法：

  with(sf.data,  
       by(geometry,
          cod_area,
          \(geometry) sum(st_area(geometry)))
  )

cod_area: 34275
[1] 625473897
----------------------------------------------------------------------------- 
cod_area: 34347
[1] 625473897