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Yes you can. You can set a different theme for each user if you want to. Take a look at this article for more information.
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What’s the difference between a Measure and a Dimension?
Dimensions are typically character based database table columns that go into the group by of the chart you are creating. These object types are used to break the data up into various groups. For example, Departments could be split into Sales, Marketing, Development etc.
Measures are typically aggregated number values that will be shown as collapsed rows of your chart e.g. Age of employee could be shown as either a 1-1 relationship with the name of a user or as an average for a Department.
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