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：
library(ggplot2)
bndBox <- data.frame(x=c(-Inf,Inf,Inf,-Inf),
y=c(Inf,Inf,-Inf,-Inf),
id="bnd")
hole <- data.frame(
x = cos(seq(0, 2*pi, length.out = 360)),
y = sin(seq(0, 2*pi, length.out = 360)),
id="circle"
)
porthole <- rbind(bndBox,hole)
ggplot() +
# 我希望能够看到这个点
geom_point(aes(x = 0,y = 0)) +
# 但不希望看到这个点
geom_point(aes(x = -1,y = 0)) +
geom_polygon(data=porthole,
aes(x = x, y = y, fill = id),
inherit.aes = FALSE)
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:
library(ggplot2)
bndBox <- data.frame(x=c(-Inf,Inf,Inf,-Inf),
y=c(Inf,Inf,-Inf,-Inf),
id="bnd")
hole <- data.frame(
x = cos(seq(0, 2*pi, length.out = 360)),
y = sin(seq(0, 2*pi, length.out = 360)),
id="circle"
)
porthole <- rbind(bndBox,hole)
ggplot() +
# I want to be able to see this point
geom_point(aes(x = 0,y = 0)) +
# But not this point
geom_point(aes(x = -1,y = 0)) +
geom_polygon(data=porthole,
aes(x = x, y = y, fill = id),
inherit.aes = FALSE)
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。
library(ggplot2)
bndBox <- data.frame(x=c(-Inf,-Inf,Inf,Inf, -Inf),
y=c(-Inf,Inf,Inf,-Inf, -Inf),
id="bnd")
bndBox <- data.frame(x=c(-1,1,1,-1, -1),
y=c(-1,-1,1,1, -1),
id="bnd")
hole <- data.frame(
x = cos(seq(0, 2*pi, length.out = 360)) * 0.95,
y = sin(seq(0, 2*pi, length.out = 360)) * 0.95,
id="circle"
)
porthole <- rbind(bndBox,hole)
ggplot() +
geom_polygon(data=porthole,
aes(x = x, y = y), fill = "red")+
geom_point(aes(x = 0, y = 0)) +
coord_fixed() +
theme_void()
<!-- -->
<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.
library(ggplot2)
bndBox <- data.frame(x=c(-Inf,-Inf,Inf,Inf, -Inf),
y=c(-Inf,Inf,Inf,-Inf, -Inf),
id="bnd")
bndBox <- data.frame(x=c(-1,1,1,-1, -1),
y=c(-1,-1,1,1, -1),
id="bnd")
hole <- data.frame(
x = cos(seq(0, 2*pi, length.out = 360)) * 0.95,
y = sin(seq(0, 2*pi, length.out = 360)) * 0.95,
id="circle"
)
porthole <- rbind(bndBox,hole)
ggplot() +
geom_polygon(data=porthole,
aes(x = x, y = y), fill = "red")+
geom_point(aes(x = 0, y = 0)) +
coord_fixed() +
theme_void()
<!-- -->
<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：
library(ggplot2)
library(sf)
bndBox <- data.frame(x=c(-1,1,1,-1),
y=c(1,1,-1,-1),
id="bnd")
hole <- data.frame(
x = cos(seq(0, 2*pi, length.out = 360)),
y = sin(seq(0, 2*pi, length.out = 360)),
id="circle"
)
portholeSF <- st_sfc(
st_polygon(
list(
hole = cbind(
c(hole$x,hole$x[1]),
c(hole$y,hole$y[1])
),
bnd = cbind(
c(bndBox$x,bndBox$x[1]),
c(bndBox$y,bndBox$y[1])
)
)
)
)
ggplot() +
# 我想看到这个点
geom_point(aes(x = 0,y = 0)) +
# 但不想看到这个点
geom_point(aes(x = -0.75,y = 0.75)) +
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:
library(ggplot2)
library(sf)
bndBox <- data.frame(x=c(-1,1,1,-1),
y=c(1,1,-1,-1),
id="bnd")
hole <- data.frame(
x = cos(seq(0, 2*pi, length.out = 360)),
y = sin(seq(0, 2*pi, length.out = 360)),
id="circle"
)
portholeSF <- st_sfc(
st_polygon(
list(
hole = cbind(
c(hole$x,hole$x[1]),
c(hole$y,hole$y[1])
),
bnd = cbind(
c(bndBox$x,bndBox$x[1]),
c(bndBox$y,bndBox$y[1])
)
)
)
)
ggplot() +
# I want to see this point
geom_point(aes(x = 0,y = 0)) +
# But not this point
geom_point(aes(x = -0.75,y = 0.75)) +
geom_sf(data = portholeSF)
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