Instructor: Jing Gong. Class Time: M/W/F 2:00-2:50 pm

Assignment #5 Hints – A Checklist

Dear R experts,

While working on Assignment #5, you may experience errors. In order to at least run the script without error messages, you often have to “debug” to fix the errors.

Here is a list of things you can check:

1. Error Message. If you get an error message like this:

Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
  cannot open file 'OnTimeAirport-Jan14.csv': No such file or directory

ask yourself the following questions:

  • Did you have all the files (both Descriptives.r file and OnTimeAirport-Jan14.csv file) in the same directory/folder?
  • Are the file names correct? Sometimes when you download the file to your disk multiple times, the system automatically rename the files (like OnTimeAirport-Jan14(1).csv). If this is the case, you have to change the name back.
  • Did you set the working directory to source file location? (How to do that? Read instructions on ICA #9)

2. Changing Variable Values. Under the VARIABLES section, did you change the following variable values accordingly for the new dataset?


3. Package Installation. Were you able to install the “psych” package?
If not, check the solutions here: Problems Installing Packages?

4. Modifying R Script. In the original Descriptives.r file, our analysis was based on the NBA data. Specifically, we looked at two columns, dataSet$Salary and dataSet$Position. For the assignment, because we are using a different dataset called OnTimeAirport-Jan14.csv, you need to make the following changes accordingly:

  • Do a thorough search of your r script and make sure that you changed all places with dataSet$Salary and dataSet$Position to the new columns we are interested in in the new dataset.
  • Make sure that you changed line 87:
subset <- dataSet[ which(dataSet$Position=='PG' |  dataSet$Position=='SF'), ];


subset <- dataSet[ which(dataSet$Origin=='PHL' |  dataSet$Originn=='PIT'), ];

The reason is that now we are interested in looking at Philadelphia and Pittsburgh as origin airports (as asked in Question 5 of the answer sheet).

  • Make sure that “dataSet” has the right cases (i.e., the letter “S” should be in upper case). This is because R is case-sensitive.

If you have everything listed above checked, you should be able to at least complete the first six steps on the assignment.

5. Adding More Commands. To complete Steps 7-9, you should add a few more lines in between the t.test() and the sink() functions. More specifically, I recommend you to add lines right before the following line (line 95 of the original Descriptives.r file).

# This stops R from writing any more to the text output file.

That’s all I can think of so far. Good luck!

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