Calculating the % difference between the first and last price by date field

[Witek]

Hello guys!

I’m stuck and hope for your help, as I tried to find a reply to my question everywhere, but non of the solutions seems to work.

I am using Looker Studio to analyze the purchase price changes of various articles used for the end-product manufacturing in my company over time and react quickly and adjust the prices of our products accordingly. 

While I can easily calculate the maximum and minimum price of the products within given time range, I can not find a way to calculate a difference between the first and the last price to simply know in one field whether it’s an increase or decrease of the price. 

From what I’ve learned the only way to achieve it is to blend the data source with itself and add so custom fields selecting the last and first row, but so far I had no luck in making this work.

Please help! 🙂