在 ggplot 中为多边形创建一个孔以用作遮罩。

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英文:

R make a hole in a polygon for a ggplot mask

问题

我正在为一个 ggplot 制作一个遮罩。如何在不使用 GIS 过程的情况下删除在 ggplot 上绘制的圆内部的区域？我有一个用于在图表上创建边界框和圆的 data.frame，如下所示：

  1. library(ggplot2)
  2. bndBox <- data.frame(x=c(-Inf,Inf,Inf,-Inf),
  3.                      y=c(Inf,Inf,-Inf,-Inf),
  4.                      id="bnd")
  6. hole <- data.frame(
  7.   x = cos(seq(0, 2*pi, length.out = 360)),
  8.   y = sin(seq(0, 2*pi, length.out = 360)),
  9.   id="circle"
  10. )
  12. porthole <- rbind(bndBox,hole)
  14. ggplot() + 
  15.   # 我希望能够看到这个点
  16.   geom_point(aes(x = 0,y = 0)) +
  17.   # 但不希望看到这个点
  18.   geom_point(aes(x = -1,y = 0)) +
  19.   geom_polygon(data=porthole, 
  20.                aes(x = x, y = y, fill = id),
  21.                inherit.aes = FALSE)

在 ggplot 中为多边形创建一个孔以用作遮罩。

英文:

i'm making a mask for a ggplot. How can I delete the area inside a circle drawn over a ggplot without using GIS procedures? I have a data.frame used to make a bounding box over a plot and a circle, as follows:

  1. library(ggplot2)
  2. bndBox &lt;- data.frame(x=c(-Inf,Inf,Inf,-Inf),
  3.                      y=c(Inf,Inf,-Inf,-Inf),
  4.                      id=&quot;bnd&quot;)
  6. hole &lt;- data.frame(
  7.   x = cos(seq(0, 2*pi, length.out = 360)),
  8.   y = sin(seq(0, 2*pi, length.out = 360)),
  9.   id=&quot;circle&quot;
  10. )
  12. porthole &lt;- rbind(bndBox,hole)
  14. ggplot() + 
  15.   # I want to be able to see this point
  16.   geom_point(aes(x = 0,y = 0)) +
  17.   # But not this point
  18.   geom_point(aes(x = -1,y = 0)) +
  19.   geom_polygon(data=porthole, 
  20.                aes(x = x, y = y, fill = id),
  21.                inherit.aes = FALSE)

在 ggplot 中为多边形创建一个孔以用作遮罩。

答案1

得分: 1

已更新的答案考虑到，顺时针进行的封闭多边形形成一个孔。

  2. library(ggplot2)
  4. bndBox &lt;- data.frame(x=c(-Inf,-Inf,Inf,Inf, -Inf),
  5.                      y=c(-Inf,Inf,Inf,-Inf, -Inf),
  6.                      id=&quot;bnd&quot;)
  8. bndBox &lt;- data.frame(x=c(-1,1,1,-1, -1),
  9.                      y=c(-1,-1,1,1, -1),
  10.                      id=&quot;bnd&quot;)
  12. hole &lt;- data.frame(
  13.   x = cos(seq(0, 2*pi, length.out = 360)) * 0.95,
  14.   y = sin(seq(0, 2*pi, length.out = 360)) * 0.95,
  15.   id=&quot;circle&quot;
  16. )
  19. porthole &lt;- rbind(bndBox,hole)
  21. ggplot() + 
  22.   geom_polygon(data=porthole, 
  23.                aes(x = x, y = y), fill = &quot;red&quot;)+
  24.   geom_point(aes(x = 0, y = 0)) +
  25.   coord_fixed() +
  26.   theme_void()

在 ggplot 中为多边形创建一个孔以用作遮罩。<!-- -->

<sup>Created on 2023-06-15 with reprex v2.0.2</sup>

英文:

Updated answer to take into account that a closed polygon progressing clockwise forms a hole.

  2. library(ggplot2)
  4. bndBox &lt;- data.frame(x=c(-Inf,-Inf,Inf,Inf, -Inf),
  5.                      y=c(-Inf,Inf,Inf,-Inf, -Inf),
  6.                      id=&quot;bnd&quot;)
  8. bndBox &lt;- data.frame(x=c(-1,1,1,-1, -1),
  9.                      y=c(-1,-1,1,1, -1),
  10.                      id=&quot;bnd&quot;)
  12. hole &lt;- data.frame(
  13.   x = cos(seq(0, 2*pi, length.out = 360)) * 0.95,
  14.   y = sin(seq(0, 2*pi, length.out = 360)) * 0.95,
  15.   id=&quot;circle&quot;
  16. )
  19. porthole &lt;- rbind(bndBox,hole)
  21. ggplot() + 
  22.   geom_polygon(data=porthole, 
  23.                aes(x = x, y = y), fill = &quot;red&quot;)+
  24.   geom_point(aes(x = 0, y = 0)) +
  25.   coord_fixed() +
  26.   theme_void()

在 ggplot 中为多边形创建一个孔以用作遮罩。<!-- -->

<sup>Created on 2023-06-15 with reprex v2.0.2</sup>

答案2

得分: 0

我可以使用 sf 做我想做的事情，但希望不要走这条路，因为我发现代码难以理解，感觉像是 geom_polygon() 应该能够处理它。以下是一个繁琐的解决方案：

  1. library(ggplot2)
  2. library(sf)
  4. bndBox <- data.frame(x=c(-1,1,1,-1),
  5.                      y=c(1,1,-1,-1),
  6.                      id="bnd")
  7. hole <- data.frame(
  8.   x = cos(seq(0, 2*pi, length.out = 360)),
  9.   y = sin(seq(0, 2*pi, length.out = 360)),
  10.   id="circle"
  11. )
  13. portholeSF <- st_sfc(
  14.   st_polygon(
  15.     list(
  16.       hole = cbind(
  17.         c(hole$x,hole$x[1]), 
  18.         c(hole$y,hole$y[1])
  19.       ),
  20.       bnd = cbind(
  21.         c(bndBox$x,bndBox$x[1]), 
  22.         c(bndBox$y,bndBox$y[1])
  23.       )
  24.     )
  25.   )
  26. )
  28. ggplot() + 
  29.   # 我想看到这个点
  30.   geom_point(aes(x = 0,y = 0)) +
  31.   # 但不想看到这个点
  32.   geom_point(aes(x = -0.75,y = 0.75)) +
  33.   geom_sf(data = portholeSF)

请注意，我只翻译了代码的注释和文字内容，代码本身没有翻译。

英文:

I can do what I want with sf but was hoping not to go down this road as I find the code hard to follow and feel like geom_polygon() should be able to handle it. Here is a cumbersome solution:

  1. library(ggplot2)
  2. library(sf)
  4. bndBox &lt;- data.frame(x=c(-1,1,1,-1),
  5.                      y=c(1,1,-1,-1),
  6.                      id=&quot;bnd&quot;)
  7. hole &lt;- data.frame(
  8.   x = cos(seq(0, 2*pi, length.out = 360)),
  9.   y = sin(seq(0, 2*pi, length.out = 360)),
  10.   id=&quot;circle&quot;
  11. )
  14. portholeSF &lt;- st_sfc(
  15.   st_polygon(
  16.     list(
  17.       hole = cbind(
  18.         c(hole$x,hole$x[1]), 
  19.         c(hole$y,hole$y[1])
  20.       ),
  21.       bnd = cbind(
  22.         c(bndBox$x,bndBox$x[1]), 
  23.         c(bndBox$y,bndBox$y[1])
  24.       )
  25.     )
  26.   )
  27. )
  29. ggplot() + 
  30.   # I want to see this point
  31.   geom_point(aes(x = 0,y = 0)) +
  32.   # But not this point
  33.   geom_point(aes(x = -0.75,y = 0.75)) +
  34.   geom_sf(data = portholeSF)

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  • 本文由 发表于 2023年6月16日 05:42:37
  • 转载请务必保留本文链接：https://go.coder-hub.com/76485708.html
  • ggplot2
  • r
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