Hi Anitha,
Follow below steps:
1. Create a calculated field to find the total avg for subcategory using Fixed LOD.
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2. Create another calculated field to create comparison using Exclude LOD.
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3. Now drop the above field and avg(sales) in the sheet.
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4. Drop avg(sales) in to label and below Chart would be shown. The image shows category sales and difference with respect to total average.
( Green bar shows required comparison using exclude lod and red shows avg for each subcategory )
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5. To show more difference i have also added a dual axis beside to show the comparison. ( Orange show the total avg and blue shows avg for each subcategory )
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Hope this helps you.