b<-ggplot(data,aes(x=index,y=Cerebellum)) b+geom_point(size=2,color='blue')+ coord_fixed()+theme_classic()+ geom_smooth(method = "lm",formula = y ~ x,size=2,color="black",fill="green")+ theme (aspect.ratio=1,axis.text.x = element_text (size = 15),axis.title.x = element_text (size = 15),axis.title.y = element_text(size = 15),axis.text.y = element_text (size = 15))+ stat_cor(data=data, method = "pearson")将代码中输出的相关系数和显著性水平设为显示三位小数

可以将`format`函数的`digits`参数设置为3，以保留三位小数。修改后的代码如下所示：

b <- ggplot(data, aes(x = index, y = Cerebellum))
b + geom_point(size = 2, color = 'blue') + coord_fixed() + theme_classic() +
geom_smooth(method = "lm", formula = y ~ x, size = 2, color = "black", fill = "green") +
theme(aspect.ratio = 1, axis.text.x = element_text(size = 15),
axis.title.x = element_text(size = 15), axis.title.y = element_text(size = 15),
axis.text.y = element_text(size = 15)) +
stat_cor(data = data, method = "pearson", label.x.npc = 0.8, label.y.npc = 0.9,
         cor.label = paste("r = ", format(cor(data$x, data$y), digits = 3), ", p =",
                            format(cor.test(data$x, data$y)$p.value, digits = 3)))

在`stat_cor`函数中，`cor.label`参数的值使用`paste`函数将相关系数和显著性水平拼接成一个字符串，并使用`format`函数将相关系数和显著性水平的小数位数都设为3。这样就可以在散点图中显示保留三位小数的相关系数和显著性水平了。