R：显示多边形几何体特征列表

我目前正试图找到多边形列表的面积、X形心、Y形心和周长。为了测试这一点，我使用了GISTools包中的Georgia数据。具体来说，我使用的是由159个多边形组成的

georgia.polys

列表

到目前为止，该守则的内容如下：

>library(GISTools)
>data(georgia)

面积：

>polygon.area <- function(co_ord){
  n = dim(co_ord)[1] 
  sum.of = 0
  for(i in 1:(n-1)){
    sum.of = sum.of + (co_ord[i,1]*co_ord[i+1,2])-(co_ord[i+1,1]*co_ord[i,2])
  }
  return((sum.of*0.5)*-1)
}

返回：

  Polygon Area Centroid of X Centroid of Y Perimeter
1    891511462       1240651      999300.7  156744.9

然而，当尝试获取多边形几何体的完整列表时，我得到以下错误。到目前为止，我已经测试了两种方法：

>Complete.List(list(georgia.polys[[1:159]]))

返回错误：

Error in Multiple[[1:159]] : recursive indexing failed at level 2

或：

完成。列表（列表（georgia.polys））

返回错误：

Error in data.frame(c(1292287.01256335, 1292653.93730068, 1292949.41616757,  : 
  arguments imply differing number of rows: 125, 99, 53, 124, 116, 57, 88, 48, 69, 160, 107, 26, 163, 151, 287, 190, 136, 77, 93, 227, 37, 56, 30, 256, 180, 96, 32, 47, 68, 73, 64, 59, 92, 67, 87, 115, 108, 117, 43, 14, 50, 54, 91, 44, 89, 58, 205, 133, 111, 71, 72, 150, 97, 138, 75, 25, 105, 74, 95, 17, 22, 119, 155, 60, 94, 109, 42, 76, 221, 176, 106, 143, 126, 82, 24, 51, 85, 100, 128, 62, 40, 187, 35, 218, 86, 83, 114, 132, 208, 34, 65, 27, 123, 189, 171, 165, 113, 121, 137, 102 

对于如何使用相同的最终表格列出所有多边形，我有点困惑。希望这是足够的信息

谢谢， 吉姆

这个怎么样：

l <- lapply(1:length(georgia.polys), function(x) { 
  Complete.List(list(georgia.polys[[x]]))
}
)
df <- do.call(rbind, l)

---

l除非你是为了做家庭作业或练习而发明轮子，否则就使用你可以使用的工具：

library(sf)
library(GISTools)
library(tidyverse)

data(georgia)

georgia_polys <- map(georgia.polys, ~st_polygon(list(.x)))

map_df(georgia_polys, ~{
  data_frame(
    poly = list(.x),
    perimeter = st_length(.x),
    area = st_area(.x),
    centroid = list(as_data_frame(st_coordinates(st_centroid(.x))))
  ) %>% 
    unnest(centroid)
}) -> xdf

xdf
## # A tibble: 159 x 5
##        poly perimeter       area       X         Y
##      <list>     <dbl>      <dbl>   <dbl>     <dbl>
##  1 <S3: XY>  206874.1 1326077000 1288960 1056979.7
##  2 <S3: XY>  156744.9  891511462 1240651  999300.7
##  3 <S3: XY>  130088.2  740601936 1276765 1033212.9
##  4 <S3: XY>  185782.8  905136790 1093093  983270.9
##  5 <S3: XY>  151904.4  692189817 1179548 1190223.5
##  6 <S3: XY>  103520.6  605358990 1137903 1329516.0
##  7 <S3: XY>  101619.1  422588345 1123611 1286951.8
##  8 <S3: XY>  159108.3 1217187029 1017758 1301371.8
##  9 <S3: XY>  139681.3  657751019 1201770 1045931.2
## 10 <S3: XY>  178554.7 1184541018 1208139  992435.4
## # ... with 149 more rows

库（sf）
图书馆（GISTools）
图书馆（tidyverse）
数据（格鲁吉亚）
佐治亚州奥普拉斯%
unnest（质心）
})->xdf
xdf
###A tibble:159 x 5
##多边形周长面积xy
##                         
##  1   206874.1 1326077000 1288960 1056979.7
##  2   156744.9  891511462 1240651  999300.7
##  3   130088.2  740601936 1276765 1033212.9
##  4   185782.8  905136790 1093093  983270.9
##  5   151904.4  692189817 1179548 1190223.5
##  6   103520.6  605358990 1137903 1329516.0
##  7   101619.1  422588345 1123611 1286951.8
##  8   159108.3 1217187029 1017758 1301371.8
##  9   139681.3  657751019 1201770 1045931.2
## 10   178554.7 1184541018 1208139  992435.4
## # ... 还有149行

Error in Multiple[[1:159]] : recursive indexing failed at level 2

Error in data.frame(c(1292287.01256335, 1292653.93730068, 1292949.41616757,  : 
  arguments imply differing number of rows: 125, 99, 53, 124, 116, 57, 88, 48, 69, 160, 107, 26, 163, 151, 287, 190, 136, 77, 93, 227, 37, 56, 30, 256, 180, 96, 32, 47, 68, 73, 64, 59, 92, 67, 87, 115, 108, 117, 43, 14, 50, 54, 91, 44, 89, 58, 205, 133, 111, 71, 72, 150, 97, 138, 75, 25, 105, 74, 95, 17, 22, 119, 155, 60, 94, 109, 42, 76, 221, 176, 106, 143, 126, 82, 24, 51, 85, 100, 128, 62, 40, 187, 35, 218, 86, 83, 114, 132, 208, 34, 65, 27, 123, 189, 171, 165, 113, 121, 137, 102 

l <- lapply(1:length(georgia.polys), function(x) { 
  Complete.List(list(georgia.polys[[x]]))
}
)
df <- do.call(rbind, l)

library(sf)
library(GISTools)
library(tidyverse)

data(georgia)

georgia_polys <- map(georgia.polys, ~st_polygon(list(.x)))

map_df(georgia_polys, ~{
  data_frame(
    poly = list(.x),
    perimeter = st_length(.x),
    area = st_area(.x),
    centroid = list(as_data_frame(st_coordinates(st_centroid(.x))))
  ) %>% 
    unnest(centroid)
}) -> xdf

xdf
## # A tibble: 159 x 5
##        poly perimeter       area       X         Y
##      <list>     <dbl>      <dbl>   <dbl>     <dbl>
##  1 <S3: XY>  206874.1 1326077000 1288960 1056979.7
##  2 <S3: XY>  156744.9  891511462 1240651  999300.7
##  3 <S3: XY>  130088.2  740601936 1276765 1033212.9
##  4 <S3: XY>  185782.8  905136790 1093093  983270.9
##  5 <S3: XY>  151904.4  692189817 1179548 1190223.5
##  6 <S3: XY>  103520.6  605358990 1137903 1329516.0
##  7 <S3: XY>  101619.1  422588345 1123611 1286951.8
##  8 <S3: XY>  159108.3 1217187029 1017758 1301371.8
##  9 <S3: XY>  139681.3  657751019 1201770 1045931.2
## 10 <S3: XY>  178554.7 1184541018 1208139  992435.4
## # ... with 149 more rows