Problem Set 1

Visualization Process

Directions

During ANLY 512 we will be studying the theory and practice of data visualization. We will be using R and the packages within R to assemble data and construct many different types of visualizations. We begin by studying some of the theoretical aspects of visualization. To do that we must appreciate the actual steps in the process of making a visualization.

Most of us use softare to do this and have done so for so long that we have lost an appreciation for the mechanistic steps involved in accurately graphing data. We will fix that this week by creating a series of analog (meaning you draw them by hand) graphics. The visualizations you create must be numerically and visually accurate and precisely scaled. Because of that the data sets we visualize will be small.

• A couple of tips, remember that there is preprocessing involved in many graphics so you may have to do summaries or calculations to prepare, those should be included in your work.

• To ensure accuracy pay close attention to axes and labels, you will be evaluated based on the accuracy of your graphics.

The final product of your homework (this file) should include scanned or photographed images for each question below and a short summary of the process.

To submit this homework you will create the document in Rstudio, using the knitr package (button included in Rstudio) and then submit the document to your Rpubs account. Once uploaded your will submit the link to that document on Moodle.

Questions

Find the mtcars data in R. This is the dataset that you will use to create your graphics. Use that data to draw by hand graphics for the next 4 questions.

1. Draw a pie chart showing the proportion of cars from the mtcars data set that have different carb values.

# place the code to import graphics here
knitr::include_graphics("C:\\Users\\Daisy Chen\\Downloads\\Image.png")

Firstly, the value of carb variable is identified and the proportion is calculated for each category. The angle in the pie chart is determined by the proportion.

2. Draw a bar graph, that shows the number of each gear type in mtcars.

# place the code to import graphics here
knitr::include_graphics("C:\\Users\\Daisy Chen\\Downloads\\Image-1.png")

First of all, the value of Gear is found and the count of each value is calculated. Then the x axis and y axis are determined by the count.

3. Next show a stacked bar graph of the number of each gear type and how they are further divded out by cyl.

# place the code to import graphics here
knitr::include_graphics("C:\\Users\\Daisy Chen\\Downloads\\Image-9.png")

The count of each cylinder number is calculated among each gear number. Then similar to the second plot, y is determined by the count in each category.

4. Draw a scatter plot showing the relationship between wt and mpg.

knitr::include_graphics("C:\\Users\\Daisy Chen\\Downloads\\Image-8.png")

The first step is to look at the data and identify the max and min of MPG and Weight. Then according to the data, the pair of MPG and Weight is found and ploted on the scatterplot.

5. Design a visualization of your choice using the data.

knitr::include_graphics("C:\\Users\\Daisy Chen\\Downloads\\Image-5.png")

Since x variable is continuous and the value is from 1 to 6, the interval is decided to be 0.5. The frequency is calculated in each interval.Then the steps are similar to bar chart.