如何在R中导入openstreetmaps形状文件并提取经/重心? [英] How do I import an openstreetmaps shape file in R and extract lat/long centroids?

问题描述

我正在尝试使用rgdal包在R中导入一个openstreetmaps形状文件. 我下载的形状文件包含5个组成部分:

I am trying to import an openstreetmaps shape file in R using the rgdal package. The shape file I downloaded has 5 components in it:

places.cpg
places.dbf
places.prj
places.shp
places.shx

可以在以下位置访问文件:

The files can be accessed at the following location:

https://drive.google.com/open?id=0B1ITb_7lHh1EUFVfVWc4ekRfSnc

我必须执行以下操作: 1)导入形状文件 2)在多边形的情况下，提取形状的点或质心的纬度/经度 3)将经纬度对附加到dbf文件中以进行一些分析

I have to do the following: 1) Import the shape file 2) Extract lat/long of the point or centroid of shape in case of polygon 3) Attach the lat/long pair to the dbf file to do some analysis

我停留在导入本身的第一阶段，正在运行以下代码:

I am stuck in the first stage of import itself, I am running the following code:

shape1 <- readOGR(dsn = "try", layer = "places")

"try"是我的工作目录中的文件夹，上面提到的openstreetmaps中的所有5个"places"文件都位于该文件夹中.

Here 'try' is the folder in my working directory where all the 5 'places' file from openstreetmaps mentioned above are located.

执行此操作时出现以下错误:

I get the following error when doing this:

Error in readOGR(dsn = "try", layer = "places") : no features found
In addition: Warning message:
In ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv =
use_iconv,  : ogrInfo: all features NULL

我需要有关此导入的帮助.另外，如果有一种方法可以直接从一个场所形状文件中提取纬度/经度，我只需在excel中打开places.dbf文件并添加纬度/经度即可.

I need help with this import. Alternatively if there is a way to directly extract lat/long from one of the places shape file, I can just open the places.dbf file in excel and add the lat/long.

推荐答案

当您遇到readOGR()函数的问题时:另一种可能性是使用maptools包.它创建SpatialXXXDataFrames，因此您可以使用rgeos等中的所有功能.

When you are facing troubles with the readOGR() function: Another possibility is to use the maptools package. It creates SpatialXXXDataFrames so you can use all the functions from rgeosetc.

library(maptools)

setwd("/your/data/path/")

places <- readShapeSpatial("places")
# ... your geospatial functions, like
plot(places)

可能您将不得不调整空间数据的投影.对于OSM-Data，您需要在 spatialreference.org 中找到WGS84(或EPSG:4326)的proj4string.

probably you will have to adjust the projection of the spatial data. For OSM-Data you will need to find the proj4string for WGS84 (or EPSG:4326) at spatialreference.org.

因此您可以在R中调整投影:

Thus you can adjust your projection in R:

proj4string(places) <- CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs")

有关多边形质心的计算/提取"，请参见此帖子.

For the calculation/"extraction" of polygon centroids see this post.

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