Session 2: Instructions

• Choose one of the two Activities to return as homework. The other one, you can also return it for extra points.
• Write down your answers and all your code in an R script file. Save it n the scripts folder. Remember to comment the code so it is easy to understand for yourself and other.

• Send the script file to your instructor for checking/grading.

Activity 1

Reading data tables into R

After your hard work helping your colleague prepare for the 2018 field season by rearranging their data, you receive a revised dataset for 2016. Your colleague has asked that you make sure you can read in this format and work with it in R before tackling the rearrangement of the 2017 data.

1. Download the cleaned 2016 WMA bird dataset using the function download.file(), and save it to the /data directory in your working directory. The url for the file is https://raw.githubusercontent.com/ericlind/data-mgmt-4-biologists/gh-pages/data/wma-bird-data-2016.csv

2. Read in the dataset using read.csv(), and assign it to a named object.

3. Using the str() function, examine the structure of the imported dataset. Do the field types appear to be correct?

4. Type the name of the object at the console and hit enter. Is what is printed to screen useful? Explain your answer.

5. Examine the first few rows of data using the head() function. How many rows and columns does the data table have?

6. Based on the last two questions, which one is more useful, using the function head() or typing the name of the object?

7. Create a new object from only the first 100 rows of data. Use the function write.csv() to export this new object to a file called wma-bird-data-2016-first100.csv. Send this table to your instructor for grading.

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Activity 2

Run the code from the following tutorials:

• Data Frame Reference
• Data frame column vectors
• Data frame column slice
• Data frame row slice

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