在R中绘制卡方QQ图中的QQ线

Question

我将下面的代码复制到r help中。但是，qqline函数不起作用。原因何在？

library(mgcViz)
y <- rchisq(500, df = 3)
## Q-Q plot for Chi^2 data against true theoretical distribution:
qqplot(qchisq(ppoints(500), df = 3), y, main = expression("Q-Q plot for" ~~ {chi^2}[nu == 3]))
qqline(y, distribution = function(p) qchisq(p, df = 3), prob = c(0.1, 0.6), col = 2)

谢谢!

Answer 1

要使用mgcViz添加qqline，您需要使用ggplot：

library(mgcViz)
y <- rchisq(500, df = 3)
## Q-Q plot for Chi^2 data against true theoretical distribution:
qqplot(qchisq(ppoints(500), df = 3), y, main = expression("Q-Q plot for" ~~ {chi^2}[nu == 3]))

# Add qq line
library(ggplot2)
ggplot2::last_plot() + qqline(y, distribution = function(p) qchisq(p, df = 3), prob = c(0.1, 0.6), col = 2)

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要查看qqline的截距和斜率，可以执行以下操作：

my.qqline = qqline(y, distribution = function(p) qchisq(p, df = 3), prob = c(0.1, 0.6), col = 2)
> my.qqline$data
   intercept     slope
1 0.08606285 0.9290453