Pie Charts

Making a Pie Chart

The next chart to learn is the pie chart. Pie charts are used to see parts-to-whole relationships such as totaling the favorite types of movie genres out of a survey of 100 people. Pie charts divide up a circle into various slices in which each slice represents a percentage of the total variable being represented. The dataset that we will be using for this lesson describes wine reviews in which we can observe the various popular wine types.

First step to this process is that we will need to properly load in the dataset and format it. It is best to keep track of where we are storing our data files. For this tutorial, we will have our dataset inside of a Data folder contained in another internal folder called "Miscellaneous."

To follow along, we can download the wineReviews.csv dataset here.

Here is a snippet of what the dataset should look like:

Loading and Formatting

As mentioned previously, to load and read in the dataset, we will need to create a DataFrame component named "frame". Using the frame, we must use the Load function and type in the file path of the wine reviews CSV. Recall that a CSV is a comma separated text file that holds in data.

use Libraries.Compute.Statistics.DataFrame
use Libraries.Interface.Controls.Charts.PieChart

// create dataframe to read in data
DataFrame frame
frame:Load("../Data/Miscellaneous/wineReviews.csv")

Once the data has been loaded in, we will now extract this data to use in the data chart. We will be using the function, AddSelectedFactors(text header) to format our data into the pie chart. AddSelectedFactors(text header) will take in a string value that matches a column header to the dataset. For instance, we will be extracting the "variety" column from the dataset.

// pull out selected data, for this we will be categorizing by wine type
frame:AddSelectedFactors("variety")

Now it is time to create the Pie Chart which can be done with the following code. This creates a chart object from our DataFrame component, frame. The rest of this lesson, we will be using the chart object we have created to change and format the rest of our line chart.

// pull out selected data, for this we will be categorizing by wine type
frame:AddSelectedFactors("variety")
// create chart component inherited from the line chart library
PieChart chart = frame:PieChart()
chart:Display()

Labeling the Pie Chart

Pie charts are unique because there actually is no need to label an x axis or y axis. The different variables within the genre group we are using separates into parts that we can examine as a whole. For this part, we will focus on learning how to label our chart title and our legend title. Additionally, we will also change the orientation of our legend within the pie chart. The functions we would be using in this case are: SetTitle(text title), SetLegendTitle(text title), SetLegendLocationToBottom(), and SetSubtitle(text title). Here is a brief description of what each function takes in.

// create title to describe graph
chart:SetTitle("Top Wine Reviews Based on Type")

// label your legend to show users what is being categorized
chart:SetLegendTitle("Variety")
chart:SetSubtitle("Praised wine categorized by type")
// set the legend location, choices are left, right, top and bottom
chart:SetLegendLocationToBottom()

Customizing the Pie Chart

Now that we have our data labeled, we can customize our data to our liking, such as adjusting the font size, changing the color palette, and creating a hole in the middle of our pie chart. We will be playing around with all these features and to do so, we will be again, using our chart object to call these functions. The functions we will be using for this would be: SetDonutHolePercent(), SetFontSize(), and SetColorPaletteToPositive()

// creates a hole in the middle of the pie chart (optional feature)
chart:SetDonutHolePercent(0.1)

// adjust font size by preference, here we set it to 20 pt
chart:SetFontSize(20)

/* change color palette if needed, this color palette is set to 
   Colorgorical which helps give our graphs aesthetic and discriminable color palettes
*/
//chart:SetColorPaletteToNegative()
//chart:SetColorPaletteToCalm()
//chart:SetColorPaletteToMagma()
//chart:SetColorPaletteToColorgorical()
chart:SetColorPaletteToPositive()

Displaying The Chart

Congratulations, our Pie Chart is constructed! Now we can display our chart with the Display() function. There are two ways to do this, letting it automatically display and specifying a specific window size. By doing chart:Display() it will display in a size equal to the screen size. By doing chart:Display(num, num), it will display the chart in a respected constraint window size. We will be using the default display to show the histogram.

chart:Display()

Now, feel free to clean, build, and run our program and we shortly should see a Game window pop-up. This is our Pie Chart! To view the entire code, click here to view the file.

Try it Yourself!

Press the blue run button to execute the code in the code editor. Press the red stop button to end the program. Your program will work when the console outputs "Build Successful!"

Final Chart

Further Useful Pie Chart Functions

Next Tutorial

In the next tutorial, we will discuss line chart, which describes how to use the line chart in quorum.