使用this作为参考,我试图绘制一个较低的四十八个地图,并添加图层以可视化状态之间的流动。如何在ggplot地图上添加地理空间连接?
library(ggplot2)
library(maps)
library(geosphere) # to inter-polate a given pair of (lat,long) on the globe
# load map data for the US
all_states <- map_data("state")
# plot state map
p <- ggplot() + geom_polygon(data=all_states,
aes(x=long, y=lat, group = group),
colour="white", fill="grey10")
# sample origin - destination lat,long pairs
geo <- structure(list(orig_lat = c(36.17, 36.17, 36.17),
orig_lon = c(-119.7462, -119.7462, -119.7462), dest_lat = c(33.7712, 36.17, 39.0646),
dest_lon = c(-111.3877, -119.7462, -105.3272)), .Names = c("orig_lat",
"orig_lon", "dest_lat", "dest_lon"), row.names = c(NA, 3L), class = "data.frame")
#> geo
# orig_lat orig_lon dest_lat dest_lon
#1 36.17 -119.7462 33.7712 -111.3877
#2 36.17 -119.7462 36.1700 -119.7462
#3 36.17 -119.7462 39.0646 -105.3272
# list to hold a dataframe of interpolated points for each origin-destination pair
list_lines <- list()
# use the geosphere package's gcIntermediate function to generate 50 interpolated
# points for each origin-destination pair
for (i in 1:3) {
inter <- as.data.frame(gcIntermediate(c(geo[i,]$orig_lon, geo[i,]$orig_lat),
c(geo[i,]$dest_lon, geo[i,]$dest_lat),
n=50, addStartEnd=TRUE))
list_lines[i] <- list(inter)
p <- p + geom_line(data = list_lines[[i]], aes(x = lon, y = lat), color = '#FFFFFF')
}
p
这里是我所得到的,当我尝试打印情节
p
Error in eval(expr, envir, enclos) : object 'lon' not found
我试图调试这,发现这个工作
p + geom_line(data = list_lines[[1]], aes(x = lon, y = lat), color = '#FFFFFF')
但加入第二另一层list元素会破坏它,但就我对R和ggplot的有限知识而言,这是我能得到的!
这是相当愚蠢的我!解决了这个问题,谢谢! – JConnor 2012-08-05 11:40:57