14 Statistical Functions

In R’s built-in datasets library is the data frame quakes. Make sure you can access this
object and view the corresponding help file to get an idea of what this data represents.
Then, do the following:
(i) Select only those records that correspond to a magnitude (mag) of greater than or
equal to 5 and write them to a table-format file called q5.txt in an existing folder
on your machine. Use a delimiting character of! and do not include any row
names.
(ii) Read the file back into your R workspace, naming the object q5.dframe.

In the contributed package car, there’s a data frame called Duncan, which provides
historical data on perceived job prestige in 1950. Install the car package and access the
Duncan data set and its help file. Then, do the following:
(i) Write R code that will plot education on the x-axis and income on the y-axis, with
both x- and y-axis limits fixed to be [0,100]. Provide appropriate axis labels. For
jobs with a prestige value of less than or equal to 80, use a black o as the point
character. For jobs with prestige greater than 80, use a blue •.
(ii) Add a legend explaining the difference between the two types of points and then
save a 500 × 500 pixel.png file of the image.