Comparing values period by period

[#1]

Hi, guys!

I have dataset which contains years and values of some indicator. I need to calculate the difference between each year and the previous one, and show the result in the same table. Please, any ideas how to solve this issue?

[#2]

I solved the problem by using function before in a table. but how to show the same figures on the barchart? before function doesn't wotk there.