如何按纬度过滤 sf 对象? [英] How to filter a sf object by latitude?

问题描述

我有一个安大略省边界的 shapefile，内容如下:

I have a shapefile for Ontario province boundary that I read as follows:

library(sf)
library(here)
ontario <- sf::st_read(here::here("data", "messy_data", "Ontario.shp"), quiet = TRUE) %>%
  st_transform(4326)

它可以绘制如下:

我想保留 ontario 数据仅用于 latitude <51.但由于它是一个 sf 对象，dplyr::filter(latitude <51) 不起作用.我知道我可以使用 st_coordinates() 提取坐标，但是如何将它们连接回数据以过滤掉更高的高度?
或者，sf 中是否有任何函数可以用来进行过滤?我查看了帮助，但到目前为止找不到任何相关内容.

I want to keep the ontario data only for latitude < 51. But since it is a sf object, dplyr::filter(latitude < 51) doesn't work. I know that I can extract the coordinates with st_coordinates(), but how can I join them back to the data to filter out the higher altitude?
Alternatively, is there any function in sf that I could use to do the filter? I looked into the help but couldn't find anything relevant so far.

推荐答案

让我们从 GADM 数据中获取加拿大:

Let's get Canada from the GADM data:

library(raster)
library(sf)
cdn = getData("GADM",country="can",level=1)

这应该是安大略:

ont = cdn[9,]
ont$NAME_1

转换为 sf 对象:

ont = st_as_sf(ont)

现在开始 - 裁剪到北纬 51 度:

Now to business - crop to 51 degrees north:

ont_south = st_crop(ont, xmin=-180, xmax=180, ymin=-90, ymax=51)
plot(ont_south$geometry)

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