我正在尝试从一个简单的 shapefile 加载和绘制图层。这是美国的州界。我可以很好地加载它：
> library("sp","rgdal")
> shape = readOGR("/home/username/data/share/mapnik/world_boundaries/states_EPSG4326.shp", layer="states_EPSG4326")
OGR data source with driver: ESRI Shapefile
Source: "/home/username/data/share/mapnik/world_boundaries/states_EPSG4326.shp", layer: "states_EPSG4326"
with 2895 features and 9 fields
Feature type: wkbPolygon with 2 dimensions
但它无法绘制：
> plot(shape)
There were 50 or more warnings (use warnings() to see the first 50)
There were 50 or more warnings (use warnings() to see the first 50)
> warnings()
Warning messages:
1: Path drawing not available for this device
2: Path drawing not available for this device
3: Path drawing not available for this device
...
我错过了什么？绘图窗口中没有显示任何内容。此 shapefile 中只有单层。我可以在 qgis 中绘制它，我正在尝试寻找替代方案。R 似乎是一个受欢迎的选择，但到目前为止我运气不佳。我用谷歌搜索了这个警告，但没有发现任何有用的东西。
编辑： 我尝试过的每个形状文件都会收到相同的响应。这是我已验证的 shapefile 以相同的方式响应：
http://dds.cr.usgs.gov/pub/data/nationalatlas/statep010_nt00798.tar.gz
这是 sessionInfo() 的输出：
> sessionInfo()
R version 2.15.2 (2012-10-26)
Platform: x86_64-pc-linux-gnu (64-bit)
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=C
[4] LC_COLLATE=C LC_MONETARY=C LC_MESSAGES=C
[7] LC_PAPER=C LC_NAME=C LC_ADDRESS=C
[10] LC_TELEPHONE=C LC_MEASUREMENT=C LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] rgdal_0.7-22 sp_1.0-2
loaded via a namespace (and not attached):
[1] grid_2.15.2 lattice_0.20-10 tools_2.15.2
这也是一个 gentoo 系统，在 dev-lang/R 上启用了以下使用标志：
- X icu java jpeg nls openmp png readline tiff
未启用以下使用标志（未编译功能）：
- -bash-completion -cairo -doc -lapack -minimal -perl -profile -static-libs -tk"
对我来说唯一看起来可疑的两个是 cairo 和 tk，是否需要它们来进行绘图？
我以类似但不完全相同的结果从终端运行 R：
> shape = readOGR("/home/username/Downloads/state/statep010.shp", layer="statep010")
OGR data source with driver: ESRI Shapefile
Source: "/home/username/Downloads/state/statep010.shp", layer: "statep010"
with 62 features and 9 fields
Feature type: wkbPolygon with 2 dimensions
> plot(shape)
There were 50 or more warnings (use warnings() to see the first 50)
> warnings()
Warning messages:
1: In polypath(x = mcrds[, 1], y = mcrds[, 2], border = border, ... :
Path drawing not available for this device
2: In polypath(x = mcrds[, 1], y = mcrds[, 2], border = border, ... :
Path drawing not available for this device
3: In polypath(x = mcrds[, 1], y = mcrds[, 2], border = border, ... :
Path drawing not available for this device
...
