STAT 542 Homework 4:

NOTE:  The first five problems listed are required.  The last problem (which is actually from Chapter 6) is extra credit.

-Problem 6, Chapter 6 Exercises
NOTE:  The data are in the 'HELPfull' data table in the 'mosaicData' package.
HINT for (c):  The values_from argument in the pivot_wider function can specify more than one variable; for example, something like: values_from = c(variable1, variable2)

-Problem 7, Chapter 6 Exercises
HINT:  First create a data frame called ds1 obtained by reading in the .csv file located at:
https://people.stat.sc.edu/hitchcock/prob7chap6.csv

-Problem 10, Chapter 6 Exercises

HINT:  First select the teamID, yearID, HR and HRA columns and filter based on teamID=='CHN'.
HINT:  For the requested time series plot, you can mimic the plot from the Japanese reactors example in class, except with geom_line instead of geom_point.
       The plot in Section 7.5.2 in the book is another example you could mimic somewhat.

-Problem 1, Chapter 7 Exercises

-Problem 4, Chapter 7 Exercises 

NOTE:  First, run the following code in R to create a user-defined 'count_seasons' function:

# The count_seasons function takes a teamID (INCLUDING quotation marks) as its input,
# and returns an integer number of seasons played for that team as its output.
count_seasons <- function(x){
teamsum <- Teams %>%  
   group_by(teamID) %>%
   summarise(
    num_seasons=n()
    ) %>%
   filter(teamID==x)
ans <- teamsum$num_seasons
return(ans)
}


EXTRA CREDIT (Optional):
-Problem 4, Chapter 6 Exercises