Question

我有一个POLYGON几何类型的`public interfce IHandleMessage<T> where T:BaseMessage { void Handle(T msg); // do some stuff } public class HandleMessageOne:IHandleMessage<MessageOne>{ void Handle(MessageOne msg){//do something} } public class HandleMessageTwo:IHandleMessage<MessageTwo>{ void Handle(MessageTwo msg){//do something} } public class HandleMessageThree:IHandleMessage<MessageThree>{ void Handle(MessageThree msg){//do something} }`对象。我想使用分组属性（group_attr）将这些多边形聚合到MULTIPOLYGON中，并使用属性表连接新的MULTIPOLYGON对象。因此，我将得到一个sf对象，其中包含两行和三列（group_attr，second_attr，geometry）。我已经尝试使用sf - 它适用于st_cast个对象，但不适用于sfc个对象。是否可以使用sf包执行此操作？

sf

Answer 1

或：

> aggregate(df, list(df$second_attr), function(x) x[1])
Simple feature collection with 2 features and 3 fields
Attribute-geometry relationship: 0 constant, 2 aggregate, 1 identity
geometry type:  MULTIPOLYGON
dimension:      XY
bbox:           xmin: 0 ymin: 0 xmax: 5 ymax: 4
epsg (SRID):    NA
proj4string:    NA
  Group.1 group_attr second_attr                       geometry
1  forest          1      forest MULTIPOLYGON(((3 0, 3 1, 4 ...
2    lake          2        lake MULTIPOLYGON(((4 0, 4 1, 5 ...

Answer 2

基于https://github.com/r-spatial/sf/issues/634#issuecomment-365151794的新方法：

library(dplyr)

df_new <- df %>%
  group_by(group_attr) %>%
  summarise_all(first) 
df_new

Simple feature collection with 2 features and 2 fields
geometry type:  MULTIPOLYGON
dimension:      XY
bbox:           xmin: 0 ymin: 0 xmax: 5 ymax: 4
epsg (SRID):    NA
proj4string:    NA
# A tibble: 2 x 3
  group_attr second_attr                                                        geometry
       <dbl> <fct>                                                        <MULTIPOLYGON>
1       1.00 forest      (((3 0, 3 1, 4 1, 4 0, 3 0)), ((0 0, 1 4, 2 4, 3 2, 1 0, 0 0)))
2       2.00 lake                  (((4 0, 4 1, 5 1, 5 0, 4 0)), ((3 3, 4 2, 4 3, 3 3)))

Answer 3

非常hacky（或天真）的方法：

attr_table <- df %>% 
        as_data_frame() %>% 
        select(-geometry) %>% 
        unique()

new_df <- df %>% 
        group_by(group_attr) %>% 
        summarise() %>% 
        as.data.frame(.) %>% 
        left_join(., attr_table, by='group_attr')   %>% 
        st_as_sf()

new_df

Simple feature collection with 2 features and 2 fields
geometry type:  MULTIPOLYGON
dimension:      XY
bbox:           xmin: 0 ymin: 0 xmax: 5 ymax: 4
epsg (SRID):    NA
proj4string:    NA
  group_attr second_attr                       geometry
1          1      forest MULTIPOLYGON(((3 0, 3 1, 4 ...
2          2        lake MULTIPOLYGON(((4 0, 4 1, 5 ...

将POLYGON聚合到MULTIPOLYGON并保留data.frame

3 个答案: