如下做用ggplot2做p1,p2,不同的数据集，问如何将两幅图合并到一张图中，并且将legend合并。

a <-c(0.61,0.57,0.78,1.36,0.85,0.53,0.45,0.19,0.08) #names
b <-c(0.23,0.26,0.55,0.56,0.36,0.23,0.18,0.06,0.04) #mean t0
x <-c(0.64,0.6,0.81,1.4,0.89,0.55,0.48,0.22,0.09) #mean t1

       
da <- data.frame(a,b,x)
da1 <- melt(test_data56, id="x")
p0 <- ggplot(data=da1 , aes(x=x,
   y=value,group=variable,linetype=variable,color=variable, shape=variable)) + geom_line()


x1<- c(0.81,0.81)
y1<-c(0.5,0.8)
da2 <- data.frame(x1,y1)
p1<-ggplot()+geom_point(data=da2,aes(x=x1,y=y1, colour = c("blue","red")),size=c(3,3))