A dimension is used to define how data is grouped in a visualization. In the charts that we have created so far, under the My first charts sheet, we have the following fields used as chart dimension: CategoryName and Country.

The following steps depict how to create a master dimension:

1. If we are in view mode, click on the Edit button to enter the edit mode. 
2. Click on the Master items button to open the Master item pane.
3. Click on the Dimension pane to expand it.
4. Click on the Create new button in the Dimension pane to create a new dimension.
5. In the Dimension editor panel, select Country from the field list. Keep the name the same as the field name.

6. To define a default color for the dimension, use the color combo box to open the color picker and select the color yellow, which has the hex code #ffcf02.
7. Click outside the color picker to close it and return to the Dimension editor panel, as shown in the following screenshot:

8. Next, click on the Add dimension button to create the dimension in the Master library.
9. Select the CategoryName field and repeat the same steps but define the following properties:
   • Name as 'Category'
   • Dimension color as dark blue with the hex code #4477aa

Now, there are two dimensions created in the Master library, as follows:

The master dimensions created here will be used in Chapter 7, Creating Data Stories.