向ggmap添加一堆箭头 [英] Adding a bunch of arrows to a ggmap

问题描述

我正在绘制一张地图，该地图应该有一个来自数据集的多个（> 400）箭头叠加，每个箭头的起始和结束都有经纬度对。这里是使用dput的数据子集：

  df < -  structure（list（Lat = c（49.34054，49.34068， 49.34104，49.34106，
 49.34116,49.34133,49.34138,49.34144,49.34155,49.34164,49.34168，
 49.34178,49.34179,49.34187,49.34199,49.34202,49.3421,49.34219，
 49.34226,49.34236,49.3424） ，Lon = c（-117.76365，-117.76433，
 -117.76474，-117.76575，-117.76646，-117.76607，-117.76643，-117.76676，
 -117.76611，-117.76638，-117.76678，-117.76612， - 117.7671，-117.76678，
 -117.76776，-117.76745，-117.76706，-117.76815，-117.76778，-117.76762，
 -117.76812），LatEnd = c（49.3404216917208,49.3404813977525,49.3407696999527，
 49.3409218055133 ，49.3408834255181，49.3411571438575，49.3411444104952，
 49.3412068979592，49.3413453850968，49.3414853385912，49.3414067819334，
 49.3415646398153，49.3415782191525，49.3416671210859，49.341769715577，
 49.3418702688525，49.3418749917805，49.3419107724121，49.3418905356976，
 49.34210 ），LonEnd = c（-117.76319214364，
 -117.763951728004，-117.76423214535，-117.765201260725，-117.766005995062，
 -117.765592930919，-117.765831425366，-117.766367701412，-117.765558298351，
 -117.765915748408 ，-117.766324336458，-117.765721708226，-117.766709104693，
 -117.766420637063，-117.767340559198，-117.767000983228，-117.766699658212，
 -117.767827633167，-117.767235785716，-117.767302080608，-117.767699155441 
）），.Names （244L，
 263L，293L，313L，330L，351L，359L，369L，390L，409L， 414L，426L，
 427L，435L，442L，443L，448L，450L，455L，457L，459L），class =data.frame）
  

之前我曾使用过ggmap，因此这是我的第一次尝试：

  library（ggplot2）
 library（ggmap）
 
 prep < -  get_googlemap（
 center = c（-117.7670，49.34027），＃Long / lat of center ，或爱丁堡
 zoom = 17，
地图类型='混合'，＃也混合/地形/路线图/卫星
比例= 2）
 
 map < -  ggmap（prep，
 size = c（100，200 ），
 extent ='device'，
 darken = 0.5，
 legend =bottom，
 base_layer = ggplot（data = df，aes（x = Lon，y = Lat）））
 
p < -  map + 
 geom_segment（aes（xend = LonEnd，yend = LatEnd），
 arrow = arrow（length = unit（0.2，cm ），angle = 15），size = 0.3，color =white）
  

非常奇怪的结果 - 一些箭头头向错误的方向绘制。

然后我开始尝试使用geom_path。其中针对头部的方向进行了更正，但要求我分别输入数据集的每一行作为geom_path的输入。我做了一个for循环，但显然发生了什么事情是每次添加一个图层（'我'增加一个），所有先前的图层将消失。

Lons < - cbind（df $ Lon，df $ LonEnd）
Lats < - cbind（df $ Lat，df $ LatEnd）

map< ; - ggmap（prep，
size = c（100,200），
extent ='device'，
darken = 0.5，
legend =bottom，$ b $ （aes（x = Lons [b]），其中b是数据库中的数据， 10，]，y = Lats [10，]），
arrow =箭头（length =单位（0.2，cm），angle = 15），size = 0.3，color =white）

（i = 2：nrow（Lats））{
p < - p + geom_path（aes（x = Lons [i，]，y = Lats [i，]），
arrow =箭头（长度=单位（0.2，cm），角度= 15），size = 0.3，color =white）
} #i

任何帮助都将得到最多赞赏...

解决方案

^ h ere是通过将 ends =first选项添加到箭头（）调用中实现的解决方案。此外，有必要通过将 x 重新分配给 xend 等来反转分段方向。

积分归功于Google和 https ：//collab.firelab.org/svn/big-butte/forecast_tools/plotObsVectors.R $ b 您的原始代码使用 geom_segment 在标准 ggplot 图中使用时效果很好，所以我认为 ggmap 在做与箭头和分段无意识的东西。可能值得通知作者。

  library（grid）＃提供`arrow`函数。 
 
 p0 < -  ggplot（）+ 
 geom_segment（data = df，aes（x = Lon，y = Lat，xend = LonEnd，yend = LatEnd），
 arrow = arrow（））
 
 map<  -  ggmap（prep，size = c（100,200），extent =device，darken = 0.5，
 legend =bottom） 
 
 p1 < -  map + 
 geom_segment（data = df，aes（x = LonEnd，y = LatEnd，xend = Lon，yend = Lat），
 arrow = arrow （ends =first），color =white）
 
 library（gridExtra）
 ggsave（arrangeGrob（p0，p1，nrow = 1），file =plots.png ，
 width = 12，height = 6，dpi = 150）
  

I'm plotting a map, which is supposed to have an overlay of several (> 400) arrows from a dataset, which has lat/lon pairs for both start and end of each arrow. Here is a subset of the data using dput:

df <- structure(list(Lat = c(49.34054, 49.34068, 49.3409, 49.34106, 
49.34116, 49.34133, 49.34138, 49.34144, 49.34155, 49.34164, 49.34168, 
49.34178, 49.34179, 49.34187, 49.34199, 49.34202, 49.3421, 49.34219, 
49.34226, 49.34236, 49.3424), Lon = c(-117.76365, -117.76433, 
-117.76474, -117.76575, -117.76646, -117.76607, -117.76643, -117.76676, 
-117.76611, -117.76638, -117.76678, -117.76612, -117.7671, -117.76678, 
-117.76776, -117.76745, -117.76706, -117.76815, -117.76778, -117.76762, 
-117.76812), LatEnd = c(49.3404216917208, 49.3404813977525, 49.3407696999527, 
49.3409218055133, 49.3408834255181, 49.3411571438575, 49.3411444104952, 
49.3412068979592, 49.3413453850968, 49.3414853385912, 49.3414067819334, 
49.3415646398153, 49.3415782191525, 49.3416671210859, 49.341769715577, 
49.3418702688525, 49.3418749917805, 49.3419107724121, 49.3418905356976, 
49.3421097403974, 49.3419881060831), LonEnd = c(-117.76319214364, 
-117.763951728004, -117.76423214535, -117.765201260725, -117.766005995062, 
-117.765592930919, -117.765831425366, -117.766367701412, -117.765558298351, 
-117.765915748408, -117.766324336458, -117.765721708226, -117.766709104693, 
-117.766420637063, -117.767340559198, -117.767000983228, -117.766699658212, 
-117.767827633167, -117.767235785716, -117.767302080608, -117.767699155441
)), .Names = c("Lat", "Lon", "LatEnd", "LonEnd"), row.names = c(244L, 
263L, 293L, 313L, 330L, 351L, 359L, 369L, 390L, 409L, 414L, 426L, 
427L, 435L, 442L, 443L, 448L, 450L, 455L, 457L, 459L), class = "data.frame")

I've worked with ggmap before, and therefore this was my first try:

library(ggplot2)
library(ggmap)

prep <- get_googlemap(
center = c(-117.7670, 49.34027), #Long/lat of centre, or "Edinburgh"
zoom = 17, 
maptype = 'hybrid', #also hybrid/terrain/roadmap/satellite
scale = 2)

map <- ggmap(prep, 
    size = c(100, 200),
    extent='device', 
    darken = 0.5,
    legend = "bottom",
    base_layer = ggplot(data = df, aes(x = Lon, y = Lat))) 

p <- map +
    geom_segment(aes(xend = LonEnd, yend = LatEnd),
            arrow = arrow(length = unit(0.2,"cm"), angle = 15), size = 0.3, colour = "white") 

Which produced a very odd result - some of the arrows had their heads plotted in the wrong direction.

Then I proceeded to try and use geom_path instead. Which corrected for the direction of the heads, but required that I input every line of the dataset separately as input to the geom_path. I made a for loop, but apparently what happened there was that every time a layer was added ('i' upped by one), all previous layers would disappear.

Lons <- cbind(df$Lon, df$LonEnd)
Lats <- cbind(df$Lat, df$LatEnd)

map <- ggmap(prep, 
    size = c(100, 200),
    extent='device', 
    darken = 0.5,
    legend = "bottom",
    base_layer = ggplot(data = df[1,], aes(x = Lon, y = Lat))) 


p <- map + geom_path(aes(x = Lons[10,], y = Lats[10,]),
                arrow = arrow(length = unit(0.2,"cm"), angle = 15), size = 0.3, colour = "white")

for(i in 2:nrow(Lats)){
        p <- p + geom_path(aes(x = Lons[i,], y = Lats[i,]),
        arrow = arrow(length = unit(0.2,"cm"), angle = 15), size = 0.3, colour = "white") 
                } #i

Any help would be most appreciated...

解决方案

Here is a solution achieved by adding the ends="first" option to your arrow() call. Also, it is necessary to then reverse the the segment direction by reassigning x to xend, etc.

Credit goes to google and https://collab.firelab.org/svn/big-butte/forecast_tools/plotObsVectors.R

Your original code using geom_segment works fine when used in a standard ggplot plot, so I presume that ggmap is doing something unintended with the arrows and segments. It may be worth notifying the authors.

library(grid) # provides `arrow` function.

p0 <- ggplot() +
      geom_segment(data=df, aes(x=Lon, y=Lat, xend=LonEnd, yend=LatEnd),
          arrow = arrow())

map <- ggmap(prep, size=c(100, 200), extent="device", darken=0.5, 
             legend="bottom") 

p1 <- map + 
     geom_segment(data=df, aes(x=LonEnd, y=LatEnd, xend=Lon, yend=Lat), 
         arrow=arrow(ends="first"), colour="white") 

library(gridExtra)
ggsave(arrangeGrob(p0, p1, nrow=1), file="plots.png", 
    width=12, height=6, dpi=150)

这篇关于向ggmap添加一堆箭头的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！