使用 R 操作 shapefile 属性表 [英] Manipulate shapefile attribute table using R
问题描述
我已经发布了这个问题GIS 堆栈交换，但没有看到太多流量.
I've posted this question on the GIS stack exchange, but it's not seeing much traffic.
我是一名 GIS 用户，多年来一直使用 R 进行统计，我很高兴看到发布了许多新的 GIS 功能(栅格、shapefile、rgdal 等).
I'm a GIS user who's been using R for stats for a few years, and I'm excited to see a lot of new GIS capabilities being released (raster, shapefiles, rgdal, etc).
我在 R 中完成了大量的数据库和表操作，因此能够在 shapefile 中添加和删除属性是一个强大的潜力.
I've done a lot of database and table manipulation in R, so being able to add and remove attributes from shapefiles is a powerful potential.
我希望我只是错过了那里的内容，但我似乎找不到从 shapefile 属性表中添加或删除属性的好方法.
I'm hoping I'm just missing what's out there, but I can't seem to find a good method for adding or removing attributes from a shapefile attribute table.
Overflow 的任何人都可以回复我的 GIS 帖子吗?或者我可以被告知如何将我的列表属性表放入数据框中并返回以替换当前的属性表?
Can anyone from Overflow respond to my GIS post? Or can I be advised how to get my list attribute table into a dataframe and back to replace the current attribute table?
自我的原始帖子以来取得了一些进展:
Some progress since my original post:
这是在弄清楚如何获取我的属性表 appart (.dbf)，添加内容，现在我正在尝试将其重新组合起来以替换原始 dbf.
This is getting at figuring out how to take my attribute table appart (.dbf), add stuff, and now I'm trying to put it back together to replace the original dbf.
>libary(raster); library(rgdal); library(shapefiles)
>shp<-shapefile(Shape) # D.C. area airport polygons
>summary(shp) #Shapefile properties
Object of class SpatialPointsDataFrame
Coordinates:
min max
coords.x1 281314.2 337904.7
coords.x2 4288867.0 4313507.0
Is projected: TRUE
proj4string :
[+proj=utm +zone=18 +datum=WGS84 +units=m +no_defs +ellps=WGS84 +towgs84=0,0,0]
Number of points: 4
Data attributes:
ObjectID LOCID NAME FIELD STATE STATE_FIPS ACAIS TOT_ENP TYPE
Min. :134.0 Length:4 Length:4 Length:4 Length:4 Length:4 Length:4 Min. : 271 Length:4
1st Qu.:242.8 Class :character Class :character Class :character Class :character Class :character Class :character 1st Qu.: 3876 Class :character
Median :339.0 Mode :character Mode :character Mode :character Mode :character Mode :character Mode :character Median :3409113 Mode :character
Mean :310.0 Mean :3717251
3rd Qu.:406.2 3rd Qu.:7122488
Max. :428.0
>shp.AT<-read.dbf(gsub(".shp", ".dbf", Shape), header=TRUE) #Read in the attribute table from the .dbf
> shp.AT # First object in the dbf looks like an attribute table!
$dbf
ObjectID LOCID NAME FIELD STATE STATE_FIPS ACAIS TOT_ENP TYPE
1 134 ADW Andrews AFB <NA> Maryland 24 Y 5078 Military
2 279 DCA Washington National <NA> Virginia 51 Y 6813148 <NA>
3 399 HEF Manassas Regional Harry P Davis Field Virginia 51 Y 271 Regional
4 428 IAD Washington Dulles International <NA> Virginia 51 Y 8050506 International
$header
$header$file.version
[1] 3
$header$file.year
[1] 113
$header$file.month
[1] 4
$header$file.day
[1] 12
$header$num.records
[1] 4
$header$header.length
[1] 321
$header$record.length
[1] 148
$header$fields
NAME TYPE LENGTH DECIMAL
1 ObjectID N 10 0
2 LOCID C 5 0
3 NAME C 45 0
4 FIELD C 30 0
5 STATE C 24 0
6 STATE_FIPS C 2 0
7 ACAIS C 1 0
8 TOT_ENP N 11 0
9 TYPE C 20 0
>shp.tab<-as.data.frame(shp.AT[1]) # Grab the first object of the .dbf as a data.frame
> shp.tab # First list object
dbf.ObjectID dbf.LOCID dbf.NAME dbf.FIELD dbf.STATE dbf.STATE_FIPS dbf.ACAIS dbf.TOT_ENP dbf.TYPE
1 134 ADW Andrews AFB <NA> Maryland 24 Y 5078 Military
2 279 DCA Washington National <NA> Virginia 51 Y 6813148 <NA>
3 399 HEF Manassas Regional Harry P Davis Field Virginia 51 Y 271 Regional
4 428 IAD Washington Dulles International <NA> Virginia 51 Y 8050506 International
> shp.tab$NewAT<-1:nrow(shp.tab) # Add my new attribute
> shp.tab # Added my new attribute, now to get this back into my shapefile
dbf.ObjectID dbf.LOCID dbf.NAME dbf.FIELD dbf.STATE dbf.STATE_FIPS dbf.ACAIS dbf.TOT_ENP dbf.TYPE NewAT
1 134 ADW Andrews AFB <NA> Maryland 24 Y 5078 Military 1
2 279 DCA Washington National <NA> Virginia 51 Y 6813148 <NA> 2
3 399 HEF Manassas Regional Harry P Davis Field Virginia 51 Y 271 Regional 3
4 428 IAD Washington Dulles International <NA> Virginia 51 Y 8050506 International 4
>write.dbf(shp.tab, gsub(".shp", ".dbf", Shape)) # Knew this wouldn't work, but demonstrate attempt to write this object as .dbf.
ERROR:
invalid subscript type 'list'
> shp.AT[1]<-shp.tab # Try replacing the old Object[1] with my new table containing the new attribute.
> shp.AT # The table portion fo the shp.AT is gone. No attributes.
$dbf
[1] 134 279 399 428
$header
$header$file.version
[1] 3
$header$file.year
[1] 113
$header$file.month
[1] 4
$header$file.day
[1] 12
$header$num.records
[1] 4
>write.dbf(shp.AT, gsub(".shp", ".dbf", Shape)) # If I go ahead and overwrite anyway...
我的属性不见了，取而代之的是一个包含单个字段数据框"的属性表.我递归脚本再次读取属性表.
My attributes are gone and replaced with an attribute table that contains a single field "dataframe". I recurse the script to again read the attribute table.
> shp.tab
dataframe
1 134
2 279
3 399
4 428
所以，我想我很接近了.谁能帮我把它放回 shapefile 属性表?或者，有没有更好的方法?
So, I think I'm close. Can anyone help me get this back into the shapefile attribute table? Or, is there a way better method?
谢谢
推荐答案
我不确定我是否完全理解你想要做什么.看起来你只是想在属性表中添加一个新列?如果这是正确的，那么就像对待任何数据框一样对待它.
I'm not sure I totally understand what you're trying to do. It looks like you just want to add a new column to the attribute table? If this is right, then just treat it like any dataframe.
library(rgdal)
dsn <- system.file("vectors", package = "rgdal")
shp<-readOGR(dsn = dsn, layer = 'cities')
shp$NewAT<-1:nrow(shp)
这与我系统上的 shapefile 完美配合.我通常依靠 rgdal 使用 readOGR() 函数读取我的 shapefile.我相当确定您调用的 shapefile() 函数也调用了 rgdal.
This works perfectly with a shapefile I have on my system. I typically rely on rgdal to read in my shapefiles, using the readOGR() function. I'm fairly certain the shapefile() function you were calling also calls rgdal.
编辑以添加可重现的数据集.
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