Using the legend() function

The video described and illustrated the use of the legend() function to add explanatory text to a plot.

This exercise asks you to first create a scatterplot and then use this function to add explanatory text for the point shapes that identify two different data subsets.

Set up a scatterplot of Gas vs. Temp from the whiteside data frame using type = "n" option in the plot() call. Label the x-axis "Outside temperature" by specifying the xlab argument and the y-axis "Heating gas consumption" by specifying the ylab argument.
Use the which() function to create a vector indexB that points to all data observations with Insul having the value "Before".
Use the which() function to create a vector indexA that points to all data observations with Insul having the value "After".
Using the points() function, add the "Before" points to the plot, represented as solid triangles.
Using the points() function, add the "After" points to the plot, represented as open circles.
Using the legend() function, add a legend in the upper right corner of the plot with the names "Before" and "After" and the appropriate point shapes indicated.

Take Hint (-30 XP)

Exercise

Using the legend() function

Instructions