r-将一个sf对象导出到一个多形状文件中

Question

我有一个大的shapefile，需要按属性(分组值(将其拆分为多个。在ArcGIS中，此函数调用Split By Attribute。让我们从sf库中读取nc数据帧作为示例

library(tidyverse)
library(sf)
nc = st_read(system.file("shape/nc.shp", package="sf"))
nc
Simple feature collection with 100 features and 14 fields
geometry type:  MULTIPOLYGON
dimension:      XY
bbox:           xmin: -84.32385 ymin: 33.88199 xmax: -75.45698 ymax: 36.58965
epsg (SRID):    4267
proj4string:    +proj=longlat +datum=NAD27 +no_defs
First 10 features:
AREA PERIMETER CNTY_ CNTY_ID        NAME  FIPS FIPSNO CRESS_ID
1  0.114     1.442  1825    1825        Ashe 37009  37009        5
2  0.061     1.231  1827    1827   Alleghany 37005  37005        3
3  0.143     1.630  1828    1828       Surry 37171  37171       86

我想根据NAME变量将其拆分为100个形状文件。所以我要像这样去group_by，nest和walk。

nc %>% 
mutate(group = as.character(NAME)) %>% 
group_by(group) %>%
nest() %>% 
mutate(data = map(data, ~st_as_sf(.x))) %>% 
walk2(.x = data, .y = group,
~st_write(obj = .x,
dsn = paste0(.y,
".shp")))

这个漂亮的管道返回给我以下错误：

错误：无法将grouped_df/tbl_df/tbl/data.frame对象转换为函数

Answer 1

nc %>% 
mutate(group = as.character(NAME)) %>% 
group_by(group) %>%
nest() %>% 
#move walk2 inside mutate as data and group were invisibale for walk2 
#also no need for data you can ran walk2 directly 
mutate(#data = map(data, ~st_as_sf(.x)), 
txt = walk2(.x = data, .y = group, ~st_write(obj = .x, dsn = paste0(.y, ".shp"))))