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Exercise

Adding details to a plot using point shapes, color, and reference lines

Adding additional details to your explanatory plots can help emphasize certain aspects of your data. For example, by specifying the pch and col arguments to the plot() function, you can add different point shapes and colors to show how different variables or subsets of your data relate to each other. In addition, you can add a new set of points to your existing scatterplot with the points() function, and add reference lines with the abline() function.

This exercise asks you to use these methods to create an enhanced scatterplot that effectively shows how three variables in the Cars93 data frame relate to each other. These variables are:

  • Price: the average sale price for a car
  • Max.Price: the highest recorded price for that car
  • Min.Price: the lowest recorded price for that car
Instructions
100 XP
  • Use the plot() function to create a scatterplot of the Max.Price variable versus the Price variable, specifying the pch and col parameters so the data points are represented as red solid triangles. The pch value to plot solid triangles is 17.
  • Use the points() function to add a second set of points to your scatterplot, representing Min.Price versus Price, where the new data points are represented as blue solid circles. The pch value for solid circles is 16.
  • Use the abline() function to add a dashed equality reference line (i.e., a line with y-intercept 0 and slope 1). See abline() to learn what arguments a and b refer to.
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