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Visualizing Slave Voyages Data

Prepared by Brandon Locke & Dan Fandino
Maintained by LEADR under the direction of Alice Lynn McMichael

Last Updated: 12/16/2017

Finding and Evaluating Data

The Trans-Atlantic Slave Trade Database is a database of almost 36,000 slaving voyages to the Americas from between 1515 and 1866. It is not a complete database, but it represents a significant portion of them (for reference, the database includes information on almost 10 million enslaved people, while it is estimated that as many as 12 million were transported to the Americas). The project is the result of a decades-long collaboration between scholars around the Atlantic world.

For today, we have extracted the roughly 1000 slave voyages in the database that stopped in East Africa or the Indian Ocean at some point.

Download the data from here. Open the .csv file and examine the data.

Importing and visualizing with Tableau

  1. Open Tableau and click text file on the left to connect to a csv (comma separated value) file. Select eastafricanslavedata.csv and wait a minute for it to load.
  2. Once it has loaded, it should appear in the bottom half of the screen. Make sure everything looks correct.
  3. On the bottom of the screen, there will be an orange box that says “Sheet 1.” Click on that to open up a worksheet that will allow you to make some visualizations.

Where were the enslaved people of East Africa taken from and where were they headed?

On the left, you’ll see all of the data in the spreadsheets. “Dimensions” are columns with words in them - meaning there are different categories in each row.

“Measures” means that the columns have numbers in them - meaning you can rank, order, and size things according to the numbers.

This will give you a bar chart showing the total number of enslaved people who embarked from each place. We can get more detail though, so lets try another visualization.

We now have two levels of information - we can see the large segments that show how many people were taken from each East African place, and each small box within shows where those people were taken.

What are you able to see in this?

Adding Final Details

See the number of enslaved people taken from East Africa over time.

There’s a small box in the bottom left with a bar chart and a + symbol. Click that to create a new visualization.

This will give you a line chart showing the total number of enslaved people who embarked and the number that ultimately disembarked.

What are you able to see in this?

Where are enslaved people from particular places being taken?

This will give you a bar chart showing the total number of enslaved people who embarked from each place. This is a large amount of information, so let’s try to focus in on one region to get more detail.

To make the visualization easier to work with, the bar chart can be sorted in ascending or descending order using the toolbar at the top of the book.

Adding Final Details

Additional information can be added to your chart without pulling more fields into the main body.

Analyzing and Sharing

Take a moment and chat with your partner: What are you able to see from your chart? Did it look about the way you expected? Were there any surprises? Sharing your vizualizations

To share:

  1. Go to File > Save to Tableau Public As… and save the file under the name you’d like. This may require you to sign in with a (free) Tableau Public account.
  2. This will open a web browser window to your chart on the Tableau website. At the bottom, you’ll see a Share button that will give you shareable links.

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