r - Plotting in R with Points = Levels or Rownames

Question

I'm plotting mpg ~ wt in the R dataset mtcars and I want either the points replaced by the initial of the car model (rowname), or a legend with the rowname beside the points.

I don't know how to code for the first idea, and I get overlapping labels on the second. Is there a way of just labeling with the initial of the car model?

Stripped of colors, and other flourishes, here is the idea:

plot(mpg ~ wt, data = mtcars); text(wt, mpg, row.names(mtcars))

Sorry about the ugliness... BTW I tried with ggplot2... same sort of issues...

The idea behind the replacement of the points with rowname initial came from the paper on the topic of regression by Harold Henderson:

Answer 1

我会用你的简称创建一个新变量。为了这个例子，我取了每个行名的第一个字母，但显然有重叠，所以你需要手动指定一个 `legend' 列：

mtcars$legend <- substring(row.names(mtcars), 1, 1)

然后，只需添加legend作为pch参数：

plot(mpg ~ wt, data = mtcars, pch = legend)

顺便说一句，美国汽车的燃油经济性确实没有太大改善！