Lab 2: Working with Data Frames

Learning Objectives

Students will be able to:

  • Increase skill and comfort with basic data management and syntax in R
  • Create statistical graphics to answer questions about a data set
  • Understand the basic methodology and syntax of the for loop

Readings

To prepare for this lab assignment read the following tutorials

  1. Logical Statements and Applications
  2. Introduction to for-loops

Required Data and Packages

We will continue to work with the NC Births data used in Lab 1

births <- openintro::ncbirths

For descriptions of the variables in this dataset, run the command ?openintro::ncbirths

ImportantDeadline: 11/03 @ 11:59pm

Submit a single PDF for your lab report using Quarto

Section 1: Working with DataFrames

  1. What are the names of the variables that indicate whether or not the mother smoked and the weight of the baby?

  2. In addition to the variable that indicates whether or not the mother smoked, choose one numerical variable and one categorical variable that you think might also affect the weight of a baby. Explain why

  3. Create a data frame that has only the variables gender, premie, weight, and mature, and the observations for which the baby was not premature. Print out the first few rows using the head() function.

  4. Create a data frame that has only the four variables you identified in Question 1 and Question 2 and the observations for which the mother was a smoker. Print out the first few rows using the head() function

  5. Report the mean of

  1. the weights of all babies.
  2. the weights of those born to smoking mothers.
  3. the weights of those born to non-smoking mothers.

Hint: you are subsetting weights based on a condition

  1. Report the standard deviation of
  1. the weights of all babies
  2. the weights of those born to smoking mothers
  3. the weights of those born to non-smoking mothers

Section 2: Visualizing Data

  1. Using births, create two graphics that help answer this question: Does the birth weight of babies born to smoking mothers differ from those born to non-smoking mothers?

  2. Using births, create two graphics that help answer this question: Does the number of prenatal medical visits differ between mothers who smoke and those who do not?

Section 3: For loops

A researcher measures the resting heart rates (beats per minute) of 10 participants:

heart_rates <- c(72, 85, 91, 68, 105, 77, 98, 115, 83, 95)

  1. Create a vector named elevated using numeric() with the same length as heart_rates

  2. Write a for loop using seq_along() to examine each participants heart rate. Withing the loop use the logical expression heart_rates[i] > 100 to determine if the participant has an elevated heart rate or not.

  3. Print the resulting elevated vector

  4. Interpret the output of mean(elevated) in the context of the problem