Yesterday we learnt about the 'New Measure' feature in PowerBI to create new fields in desktop, rather than in PowerQuery. Here you can use DAX (the coding language used in PowerBI) to create a simple calculated field which can be used as a measure in your chart or as part of a slicer.
Follow along with this example using Superstore Sales data.
Firstly, click on your table (in my case the Orders table) in the 'Data' pane and find 'Table tools' >> 'New Measure'.
In the field below the header you can enter your DAX calculation:
Total Sales = SUM(Orders[Sales])
where
Column name = FUNCTION(Table Name[Field])
Congrats, now you've created your first DAX calculation! 😄