我有一个ggplot地图,例如:
library(ggmap)
ggmap(get_map())
我希望轴标签自动标记为N-S / W-E:例如,在上述情况下,代替lon -95.4,它应显示95.4°E。
我试图弄乱scales
包并使用scale_x_continuous
和scale_y_continuous
标签并打破选项,但我还没有设法让它发挥作用。
拥有scale_y_latitude
和scale_x_longitude
。
编辑: 感谢@Jaap的回答,我得到了以下内容:
scale_x_longitude <- function(xmin=-180, xmax=180, step=1, ...) {
ewbrks <- seq(xmin,xmax,step)
ewlbls <- unlist(lapply(ewbrks, function(x) ifelse(x < 0, paste(x, "W"), ifelse(x > 0, paste(x, "E"),x))))
return(scale_x_continuous("Longitude", breaks = ewbrks, labels = ewlbls, expand = c(0, 0), ...))
}
scale_y_latitude <- function(ymin=-90, ymax=90, step=0.5, ...) {
nsbrks <- seq(ymin,ymax,step)
nslbls <- unlist(lapply(nsbrks, function(x) ifelse(x < 0, paste(x, "S"), ifelse(x > 0, paste(x, "N"),x))))
return(scale_y_continuous("Latitude", breaks = nsbrks, labels = nslbls, expand = c(0, 0), ...))
}
哪个效果很好。但由于某些原因,我的R似乎不喜欢基点前面的度数符号......它显示为一个简单的点,例如经度-24变为24..W
答案 0 :(得分:14)
不幸的是,还没有scale_y_latitude
或# load the needed libraries
library(ggplot2)
library(ggmap)
# get the map
m <- get_map(location=c(lon=0,lat=0),zoom=5)
# create the breaks- and label vectors
ewbrks <- seq(-10,10,5)
nsbrks <- seq(-10,10,5)
ewlbls <- unlist(lapply(ewbrks, function(x) ifelse(x < 0, paste(x, "°E"), ifelse(x > 0, paste(x, "°W"),x))))
nslbls <- unlist(lapply(nsbrks, function(x) ifelse(x < 0, paste(x, "°S"), ifelse(x > 0, paste(x, "°N"),x))))
# create the map
ggmap(m) +
geom_blank() +
scale_x_continuous(breaks = ewbrks, labels = ewlbls, expand = c(0, 0)) +
scale_y_continuous(breaks = nsbrks, labels = nslbls, expand = c(0, 0)) +
theme(axis.text = element_text(size=12))
这样的事情。与此同时,这是一个预先指定标签的解决方法:
o
给出:
要获得函数中的度数,可以将scale_x_longitude <- function(xmin=-180, xmax=180, step=1, ...) {
xbreaks <- seq(xmin,xmax,step)
xlabels <- unlist(lapply(xbreaks, function(x) ifelse(x < 0, parse(text=paste0(x,"^o", "*W")), ifelse(x > 0, parse(text=paste0(x,"^o", "*E")),x))))
return(scale_x_continuous("Longitude", breaks = xbreaks, labels = xlabels, expand = c(0, 0), ...))
}
scale_y_latitude <- function(ymin=-90, ymax=90, step=0.5, ...) {
ybreaks <- seq(ymin,ymax,step)
ylabels <- unlist(lapply(ybreaks, function(x) ifelse(x < 0, parse(text=paste0(x,"^o", "*S")), ifelse(x > 0, parse(text=paste0(x,"^o", "*N")),x))))
return(scale_y_continuous("Latitude", breaks = ybreaks, labels = ylabels, expand = c(0, 0), ...))
}
ggmap(m) +
geom_blank() +
scale_x_longitude(xmin=-10, xmax=10, step=5) +
scale_y_latitude(ymin=-10, ymax=10, step=5) +
theme(axis.text = element_text(size=12))
作为上标(这将绕过对特殊符号的需要):
geom_blank
给出了以下地图:
我使用geom_point
来说明所需的效果。您当然可以使用其他geom(例如memcached -vv
)在地图上绘制数据。