[英]How to create map in R from spatial polygon given as list data type
I have a list (imported from Stata dta file) containing entries defining spacial polygons for a map, to give an idea: 我有一个列表(从Stata dta文件导入),其中包含为地图定义空间多边形的条目,以给出一个想法:
> typeof(aux3)
[1] "list"
> mode(aux3)
[1] "list"
> head(aux3)
_ID _X _Y
1 1 NA NA
2 1 -22.23933 64.56315
3 1 -22.25667 64.56053
4 1 -22.25026 64.56653
5 1 -22.27167 64.57319
6 1 -22.30311 64.55409
> tail(head(aux3,20000))
_ID _X _Y
19995 2 21.21593 60.24696
19996 2 21.21650 60.24337
19997 2 21.23972 60.24913
19998 2 21.22203 60.23304
19999 2 21.21618 60.23332
20000 2 21.22092 60.23930
> #etc.
I would like to convert this into a data structure with which I can work to create a map (without larger difficulty and without needing extensive expertise, never having done that before) in R. I inferred that the SpacialPolygons type of the sp package is the easiest choice. 我想将其转换为数据结构,利用该数据结构可以在R中创建地图(没有更大的难度并且不需要广泛的专业知识,以前从未做过)。我推断出sp包的SpacialPolygons类型是最简单的选择。 Further, from the definition, it seemed that the SpacialPolygons method (defined in this package, see the package's documentation , page 79) is the correct method to convert from list to this data type.
此外,从定义来看,似乎SpacialPolygons方法(在此程序包中定义,请参阅程序包的文档 ,第79页)是将列表转换为该数据类型的正确方法。
Unfortunately, the method is not that straightforward to work with and I need some help. 不幸的是,该方法并不是那么简单,我需要一些帮助。 My (naive) attempt yields an error that I do not understand and that does not turn up any interesting results in a google search:
我的(天真)尝试产生了一个我不理解的错误,并且在Google搜索中没有出现任何有趣的结果:
> library(maptools)
Loading required package: sp
Checking rgeos availability: FALSE
Note: when rgeos is not available, polygon geometry computations in maptools depend on gpclib,
which has a restricted licence. It is disabled by default;
to enable gpclib, type gpclibPermit()
> SP<-SpatialPolygons(aux3)
Error in SpatialPolygons(aux3) :
cannot get a slot ("area") from an object of type "integer"
Can the list above be converted to SpacialPolygon? 上面的列表可以转换为SpacialPolygon吗? If so, how?
如果是这样,怎么办? If not, what format should I choose instead?
如果没有,我应该选择哪种格式呢? Thanks.
谢谢。
If you just want to draw the map, you could use ggplot. 如果只想绘制地图,则可以使用ggplot。 I can't test this since I don't have your data, but should work.
由于我没有您的数据,因此无法测试,但应该可以。
library(ggplot2)
aux_df <- data.frame(aux3)
# as per comment: the list-to-dataframe conversion prepends the column names with X
ggplot(aux_df, aes(x=X_X, y=X_Y, group=X_ID) +
geom_polygon(color='black', fill=NA) +
coord_map() +
theme_classic()
The above assumes the list aux3
has longitude and latitude in _X
and _Y
and polygons defined by _ID
. 上面假设列表
aux3
在_X
和_Y
以及由_ID
定义的多边形中具有经度和纬度。 It applies a mercator projection by default, but you can change this using different arguments to coord_map()
. 默认情况下,它会应用墨卡托投影,但您可以使用不同的参数来更改此
coord_map()
。
Here's a working example using a map of ohio counties (arbitrary choice). 这是一个使用俄亥俄州地图(任意选择)的可行示例。
library(ggplot2)
ohio_poly <- map_data('county', region='ohio')
ggplot(ohio_poly, aes(x=long, y=lat, group=group)) +
geom_polygon(color='black', fill=NA) +
coord_map() +
theme_classic()
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