Visualizing data using a tree map

A tree map is a way of visualizing data using nested rectangles to represent hierarchical (tree-structured) data that is part of a whole. Each rectangle has an area proportional to a specific dimension of data. Different colors are often used to represent different dimensions of the data. Tree maps also make good use of space as many items can be displayed on the screen at a glance. Google Charts enables users to build tree map charts without any coding required. For our tutorial, we will use a sample data set which was obtained from the Kenya Economic Survey 2013. You can download the data set from Google Drive.

Tree map data format

For Google Drive to generate a tree map chart, your dataset must be in a particular format. Here are some guidelines:

  • The first column must be the name of an object in the hierarchy.
  • The second column must contain the name of the object’s parent. Each parent name must appear in the first column.
  • The third column must be numerical as this is what determines the size of the rectangle. It must be a positive value.
  • The optional fourth column must be numerical. It controls the color of the box.

Go to drive.google.com to upload the dataset. Click on the upload icon then from the popup menu and select Files.

Upload Data

From the File selection window that appears, browse and select the Excel file. When the file is selected, an Upload Settings dialog box appears. Ensure that the “Convert documents, presentations, spreadsheets and drawings to the corresponding Google Docs format” checkbox is selected.

Upload Settings

You can choose to select the” confirm settings” checkbox so that Google Drive will prompt you for Upload settings before each upload. Click on the Start Upload button. Google Drive will upload your file and if successful, you should be able to see your file in the list of uploaded files. See diagram below:

 

File Uploaded

Next, click on the uploaded dataset. The spreadsheet will open in Google Spreadsheet format like in the diagram below;

Open XLS File

You will notice that “All deaths” appears in the first and the second columns. The way tree maps work is that a row has to have a parent. The first row has to be the parent name. That way, all the children can be assigned portions (Nested rectangles) based on the values. The rectangles are constructed based on the first column with numbers.

Next we need to select only the data that we want to visualize. Click on row A3 (All deaths) then do not release the mouse button. Drag the mouse all the way to cell D14. Your worksheet should now look like the diagram below. Only the data that we are interested in is highlighted.

Selected Data

Click on the Insert menu then select chart.

Insert Chart

Google will automatically detect the hierarchy in your data set. By default, it will suggest a Tree map for you. It will also list for you the possible charts as per your data set structure.

Chart Types

Select the tree map chart then click on Insert. The tree map will be inserted into your spreadsheet as in the diagram below.

Chart Inserted

To further customize your chart, double click on the white space above the chart then click on the drop down arrow and select advanced edit as shown below:

Edit Chart

A dialogue box opens up where you can customize your chart. From here you can change the chart title, enable or disable scale, select levels of data, font style and customize the header and scale.

Customize Chart

More customization can be achieved by coding your tree map. A good example can be found at https://developers.google.com/chart/interactive/docs/gallery/treemap

For more information on how to customize your chart, please visit Google Drive Help

You can also watch a video on tree maps at Youtube

Daniel Cheseret
About the Author: Daniel Cheseret
Few developers in Kenya would consider applying for a data journalism fellowship but not Daniel Cheseret. Having realized that the growing importance of data journalism has created new career opportunities in the newsroom, he applied for Internews Data and Health Journalism Fellowship. I will learn more about producing infographics, data mining and creating news applications,” says the software, developer and webmaster. Among his achievements is developing a news management software for Citizen TV. While working with Royal Media Services, the company that owns Citizen TV, he developed over 10 websites for the group. After five years he left to start a consultancy firm.
Author Website: http://internewskenya.org

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