How to calculate the price gap

[#1]

Dear All QV Master,

I would like to develop a pricing gap dashboard to compare my brand pricing with my competitors brand pricing base on the input date.

I tried my best but it didn't work

Could you please give me solution with many thanks

Dashboard dimension: Input Date, Brand

Dashbaord expression: I tried with this one but it didn't work: avg(if(brandID='my brandID',_prices) - avg(if(brandID<>'my brandID',_prices)

My expectation dashborad like attached image below

Thanks very much & Best Regards,