在ggplot2中很好地安排点之间的箭头 [英] Arranging arrows between points nicely in ggplot2

问题描述

（注意 - 这与。

我沿用了代码这个：

  ggplot（points，aes（x = x，y = y））+ geom_point（aes（size = size ），color =red，shape = 1）+ 
 scale_size_continuous（range = c（4,20））+ 
 geom_segment_plus（data = trans [trans $ amount> 0.3，]，
 aes（x = x.from，y = y.from，xend = x.to，yend = y.to），
 lineend =round，arrow = arrow（length = unit（0.15，i ），
 alpha = 0.5，size = 1.3，
 offset = 0.01，shorten.start = 0.03，shorten.end = 0.03）
  pre> 
 
 
这绝对不是完美的，但它起作用 - 您可以在这里看到一个双箭头到左下角点。
 
 
 
 offset，shorten.start和shorten.end是添加的aes元素。他们可以设置为数据点，但我还没有想出如何正确扩展它们。
 
 
 
  
 
(note - this is the same piece of work as using multiple size scales in a ggplot, but I'm asking a different question) 

I'm trying to construct a plot which shows transitions from one class to another. I want to have circles representing each class, and arrows from one class to another representing transitions.

I'm using geom_segment with arrow() to draw the arrows. Is there any way to:


make the arrows stop before they reach the circles
adjust the position so that if there is an arrow in both directions, they are "dodged" rather than overlapping.


I couldn't get position="dodge" to do anything useful here.

As an example:
library(ggplot2)
points <- data.frame( x=runif(10), y=runif(10),class=1:10, size=runif(10,min=1000,max=100000) )
trans <- data.frame( from=rep(1:10,times=10), to=rep(1:10,each=10), amount=runif(100)^3 )
trans <- merge( trans, points, by.x="from", by.y="class" )
trans <- merge( trans, points, by.x="to", by.y="class", suffixes=c(".to",".from") )
ggplot( points, aes( x=x, y=y ) ) + geom_point(aes(size=size),color="red",shape=1) + 
    scale_size_continuous(range=c(4,20)) +
    geom_segment( data=trans[trans$amount>0.6,], aes( x=x.from, y=y.from, xend=x.to, yend=y.to ),lineend="round",arrow=arrow(),alpha=0.5, size=0.3)
解决方案
I've put together a simple extension of geom_segment, which allows specification of


shortening at the start and end of the lines
an amount to offset lines which share a reversed source and destination


It's up on pastebin here: geom_segment_plus.

I used code along the lines of this:
ggplot( points, aes( x=x, y=y ) ) + geom_point(aes(size=size),color="red",shape=1) +
    scale_size_continuous(range=c(4,20)) + 
    geom_segment_plus( data=trans[trans$amount>0.3,], 
        aes( x=x.from, y=y.from, xend=x.to, yend=y.to ),
        lineend="round",arrow=arrow(length=unit(0.15, "inches")),
        alpha=0.5, size=1.3, 
        offset=0.01, shorten.start=0.03, shorten.end=0.03)
It's definitely not perfect, but it works - you can see a double arrow going to the bottom left point here.

offset, shorten.start and shorten.end are the aes elements added. They can be set to data points, but I haven't figured out how to scale them properly.



                        
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