答读者问~R语言ggplot2添加拟合曲线并给指定点添加注释

用户7010445

发布于 2021-03-15 09:52:08

1.4K0

发布于 2021-03-15 09:52:08

文章被收录于专栏：小明的数据分析笔记本

image.png

昨天收到了公众号一位读者的邮件，今天的推文回答一下开头提到的问题。还是使用昨天推文的示例数据：3个品种小麦种子的7个不同的指标，这7个指标分别是

A 面积
B 周长
C紧凑度
LK 长度
WK 宽度
A_coef 偏度系数
LKG 腹沟长度

使用周长和面积构建拟合方程

首先是读入数据

seed <- read.csv("kaggle/Seed_Data.csv",header=T)
names(seed) <- c("Area", "Perimeter", "Compactness", "Length", "Width", "Asymetry.coef", "Grove.length", "Type")
head(seed)
seed$Type <- as.factor(seed$Type)

拟合方程

fitted.model<-lm(Area~Perimeter,data = seed)
summary(fitted.model)

image.png

接下来是使用ggplot2画图

library(ggplot2)
ggplot()+
  geom_point(data=seed,aes(x=Perimeter,y=Area),
             size=5,color="red",alpha=0.3)+
  geom_abline(intercept = fitted.model$coefficients[[1]],
              slope = fitted.model$coefficients[[2]],
              size=2,color="blue",alpha=0.8)+
  theme_bw()

image.png

添加你和曲线的函数是geom_abline()，直接指定斜率slope和截距intercept

接下来是添加辅助线

他的问题是拟合曲线和y=1相交，根据我自己的实际数据，比如y=15这里相交，首先在y=15这里添加水平线，使用到的是geom_hline()函数

ggplot()+
  geom_point(data=seed,aes(x=Perimeter,y=Area),
             size=5,color="red",alpha=0.3)+
  geom_abline(intercept = fitted.model$coefficients[[1]],
              slope = fitted.model$coefficients[[2]],
              size=2,color="blue",alpha=0.8)+
  theme_bw()+
  geom_hline(yintercept = 15,lty="dashed")

image.png

接下来算一下交点位置的坐标

b<-fitted.model$coefficients[[1]]
a<-fitted.model$coefficients[[2]]

fitted.curve<-function(y){
  return((y-b)/a)
}
fitted.curve(15)

在这个交点添加一个点

ggplot()+
  geom_point(data=seed,aes(x=Perimeter,y=Area),
             size=5,color="red",alpha=0.3)+
  geom_abline(intercept = fitted.model$coefficients[[1]],
              slope = fitted.model$coefficients[[2]],
              size=2,color="blue",alpha=0.8)+
  theme_bw()+
  geom_hline(yintercept = 15,lty="dashed")+
  geom_point(aes(x=fitted.curve(15),y=15),size=6,shape=17,
             color="green",alpha=0.9)

image.png

在交点位置向下添加垂直线段

ggplot()+
  geom_point(data=seed,aes(x=Perimeter,y=Area),
             size=5,color="red",alpha=0.3)+
  geom_abline(intercept = fitted.model$coefficients[[1]],
              slope = fitted.model$coefficients[[2]],
              size=2,color="blue",alpha=0.8)+
  theme_bw()+
  geom_hline(yintercept = 15,lty="dashed")+
  annotate(geom = "segment",x=fitted.curve(15),
           xend = fitted.curve(15),y=15,yend = -Inf,
           lty="dashed")+
  geom_point(aes(x=fitted.curve(15),y=15),size=6,shape=17,
             color="green",alpha=0.9)

image.png

在X轴与垂直线段的交点处添加文字

ggplot()+
  geom_point(data=seed,aes(x=Perimeter,y=Area),
             size=5,color="red",alpha=0.3)+
  geom_abline(intercept = fitted.model$coefficients[[1]],
              slope = fitted.model$coefficients[[2]],
              size=2,color="blue",alpha=0.8)+
  theme_bw()+
  geom_hline(yintercept = 15,lty="dashed")+
  annotate(geom = "segment",x=fitted.curve(15),
           xend = fitted.curve(15),y=15,yend = -Inf,
           lty="dashed")+
  geom_point(aes(x=fitted.curve(15),y=15),size=6,shape=17,
             color="green",alpha=0.9)+
  annotate(geom = "text",x=fitted.curve(15),y=11,
           label=round(fitted.curve(15),2),
           vjust=6,color="red")+
  coord_cartesian(clip = "off")