It depends how you want the bars separated. However, if you have a dimension/field that you know you want the view to be divided into, place it on the color shelf, with the measure on the rows/columns shelf.
Hope this helps!
Thanks for your reply. I have 5 measures which represented in a bar chart. I want to separate each bar into quartiles and would like to have each piece of bar in different color. Unfortunately, I dont have any other field.
I am not sure if this can be done using calculated fields. Please let me know if we have any other way.