R：线函数不生成一条线

Question

我想在我的直方图中添加密度曲线。

这是我的代码：

    privateCollege <- data.frame(filter(college.df, Private == "Yes"))
    publicCollege <- data.frame(filter(college.df, Private == "No"))
    hist(privateCollege$PhD, main = "PhD holder in Private Colleges")
    hist(publicCollege$PhD, main = "PhD holder in Public Colleges")
    line(density(privateCollege$PhD, adjust = 2))

我期待我的代码的最后一行给我直方图“私立大学的博士学位”的密度曲线，但这是我得到的：

    Call:
    line(density(privateCollege$PhD, adjust = 2))

    Coefficients:
    [1]  9.124e-04  5.808e-05

我的直方图是正确的而不是密度曲线。有人可以帮帮我吗？先感谢您！

Answer 1

问题很可能是R默认情况下绘制计数/频率直方图，请参阅https://stats.stackexchange.com/questions/169061/why-is-my-density-plot-just-a-line-on-the-bottom，因此您需要在freq=FALSE调用中设置hist，即：

    privateCollege <- data.frame(filter(college.df, Private == "Yes"))
    publicCollege <- data.frame(filter(college.df, Private == "No"))
    hist(privateCollege$PhD, main = "PhD holder in Private Colleges", freq=FALSE)
    hist(publicCollege$PhD, main = "PhD holder in Public Colleges", freq=FALSE)
    lines(density(privateCollege$PhD, adjust = 2))

另见https://stat.ethz.ch/R-manual/R-devel/library/graphics/html/hist.html

编辑：除了需要设置freq=FALSE，你的代码中也有一个拼写错误，你需要使用函数lines，理想情况下选项type="l"