R 两条线从一条线到另一条线的图

Question

我想在普通图中绘制一些点并将这些点链接到显示在它下面的 map 。我想要的基本上是 (这里我手动添加了链接) :


我应该以某种方式使用 segments与 pdt=T写在边距之外，但我不确定我需要做什么数学变换才能为进入 map 的线段末端设置正确的坐标。

我更喜欢使用传统的 plot功能和不是 ggplot2
这里是用于绘制示例的源代码(警告加载开放的街道 map 可能需要一些时间):

library(OpenStreetMap)
#Random point to plot in the graph
fdata=cbind.data.frame(runif(12),runif(12),c(rep("A",4),rep("B",4),rep("C",4)))
colnames(fdata)=c("x","y","city")

#random coordinate to plot in the map
cities=cbind.data.frame(runif(3,4.8,5),runif(3,50.95,51),c("A","B","C"))
colnames(cities)=c("long","lat","name")

#city to color correspondance
color=1:length(cities$name)
names(color)=cities$name


maxlat=max(cities$lat)
maxlong=max(cities$long)
minlat=min(cities$lat)
minlong=min(cities$long)

#get some open street map
map = openmap(c(lat=maxlat+0.02,long=minlong-0.04 ) ,
              c(lat=minlat-0.02,long=maxlong+.04) ,
              minNumTiles=9,type="osm")
longlat=openproj(map) #Change coordinate projection


par(mfrow=c(2,1),mar=c(0,5,4,6))

plot( fdata$y ~ fdata$x ,xaxt="n",ylab="Comp.2",xlab="",col=color[fdata$city],pch=20)
axis(3)
mtext(side=3,"-Comp.1",line=3)
par(mar=rep(1,4))

#plot the map
plot(longlat,removeMargin=F)
points(cities$lat ~ cities$long, col= color[cities$name],cex=1,pch=20)
text(cities$long,cities$lat-0.005,labels=cities$name)

Answer 1

网格 图形系统(它是 lattice 和 ggplot2 图形包的基础)比 R 的基本图形系统更适合这种操作。不幸的是，您的两个图都使用基本图形系统。不过幸运的是，一流的网格库 包提供允许在两个系统之间进行转换的功能。

在下面(从您对 par(mfrow=c(2,1),...) 的调用开始)，我用注释标记了我添加的行，表明它们是 My addition .关于此策略的另一个更简单的示例，see here .

library(grid)      ## <-- My addition
library(gridBase)  ## <-- My addition

par(mfrow=c(2,1),mar=c(0,5,4,6))
plot(fdata$y ~ fdata$x, xaxt = "n", ylab = "Comp.2", xlab = "",
     col = color[fdata$city],pch=20)
vps1 <- do.call(vpStack, baseViewports()) ## <-- My addition
axis(3)
mtext(side = 3,"-Comp.1",line=3)
par(mar = rep(1,4))

#plot the map
plot(longlat,removeMargin=F)
vps2 <- do.call(vpStack, baseViewports()) ## <-- My addition
points(cities$lat ~ cities$long, col= color[cities$name],cex=1,pch=20)
text(cities$long,cities$lat-0.005,labels=cities$name)

## My addition from here on out...    

## A function that draws a line segment between two points (each a
## length two vector of x-y coordinates), the first point in the top
## plot and the second in the bottom plot.
drawBetween <- function(ptA, ptB, gp = gpar()) {
    ## Find coordinates of ptA in "Normalized Parent Coordinates"
    pushViewport(vps1)
    X1 <- convertX(unit(ptA[1],"native"), "npc")
    Y1 <- convertY(unit(ptA[2],"native"), "npc")
    popViewport(3)
    ## Find coordinates of ptB in "Normalized Parent Coordinates"
    pushViewport(vps2)
    X2 <- convertX(unit(ptB[1],"native"), "npc")
    Y2 <- convertY(unit(ptB[2],"native"), "npc")
    popViewport(3)
    ## Plot line between the two points
    grid.move.to(x = X1, y = Y1, vp = vps1)
    grid.line.to(x = X2, y = Y2, vp = vps2, gp = gp)
}

## Try the function out on one pair of points
ptA <- fdata[1, c("x", "y")]
ptB <- cities[1, c("long", "lat")]
drawBetween(ptA, ptB, gp = gpar(col = "gold"))

## Using a loop, draw lines from each point in `fdata` to its
## corresponding city in `cities`
for(i in seq_len(nrow(fdata))) {
    ptA <- fdata[i, c("x", "y")]
    ptB <- cities[match(fdata[i,"city"], cities$name), c("long", "lat")]
    drawBetween(ptA, ptB, gp = gpar(col = color[fdata[i,"city"]]))
}