在R中为网格箭头指定gpar设置 [英] Specifying gpar settings for grid arrows in R

问题描述

我正在开发一个比例大小的箭头图，并且有一个大小，方向和箭头大小的工作流程，但箭头有两个问题：1.它们具有圆角连接和2。即使当 type ='closed'时，它们也不会关闭（见右下角）。

  require（ggplot2）
 require（grid）
d = data.frame（x = 1:10，y = 0，size = 1:10）
 
 ggplot（d，aes（x，y，size = size））+ 
 geom_segment（aes（xend = x，yend = y + size），
 arrow = arrow（length = unit size），mm），type ='closed'））+ 
 scale_size（range = c（2,4））
  

箭头基于，并且做出以下改动，你将以可爱的尖头箭头结束：

1 require（proto）

2添加 ggplot ::: 在GeomSegment的第一行（当前是第51行），如下所示：

GeomSegment < - proto（ggplot ::: Geom，{

<3>在 segmentsGrob 中添加参数 linejoin ='miter'至 gpar （第23行）：

lwd = size * .pt，lty = linetype，lineend = lineend，linejoin ='miter'），
$ b $ p
$ b

运行这两个函数，您将得到：



I'm developing a plot of proportionally sized arrows, and have a workflow for size, direction and arrow-head size, but there are a couple of issues with the arrowheads: 1. they have rounded line-join and 2. they don't close (see bottom right corner) even when type='closed'.

require(ggplot2)
require(grid)
d = data.frame(x = 1:10, y = 0, size = 1:10)

ggplot(d, aes(x, y, size = size)) +
  geom_segment(aes(xend = x, yend = y + size), 
               arrow = arrow(length = unit(d$size, "mm"), type='closed')) +
  scale_size(range = c(2, 4))

Arrows are based on grid graphics, but I cannot figure out how to specify the setting. get.gpar() yields:

$lineend
[1] "round"

$linejoin
[1] "round"

but gpar(linejoin = 'mitre', lineend = 'butt') does not change this. Is there any way to change these settings? Thanks in advance.

---

Edit

Plot image including grid.segments arrow added:

解决方案

Found a solution (credit to @baptiste for the pointer). If you use the geom_segment source code in github and make the following alterations you will end up with lovely pointy arrowheads:

1 require(proto)

2 add ggplot::: in first line of GeomSegment (currently line 51) as follows:

GeomSegment <- proto(ggplot:::Geom, {

3 add argument linejoin = 'mitre' to gpar in segmentsGrob (line 23):

lwd=size * .pt, lty=linetype, lineend = lineend, linejoin = 'mitre'),

Run both functions and you'll end up with:

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