如何在R中的y轴上有选择地放置重叠点

Question

我想知道如何使分类变量在图中以一定顺序出现？现在，y = YZ处的绿点为（1,1），但y = YZ处的绿点更像（1,2.2）。我想确切地在（1，YZ）上。

如何指定我的点的确切坐标？

任何帮助将不胜感激！

 x<- c("1","1","1","1","1")

    y <- c("XY","XY","XY","YZ","YZ")

    z <- c("Treatment 1","Treatment 2","Treatment 3","Treatment 1","Treatment 2")

    data<- data.frame (x,y,z)

    ggplot(data=data,aes (x=y, y=x, color = z)) + 
    coord_flip() +
    geom_point(pch = 16, size = 3, position = position_dodge(width = 0.2)) +
    xlab("ID") +
    ylab("Time") + 
    theme(axis.text.x = element_text(angle = 90, hjust = 1, vjust=0.5))