Math operations in tables

[emrekaya]

Hi all, 

I have a problem with one of my tables. I want to make some calculation between the same materials which is belonged to different dates. By this way, my intention is to find decrease or increase in prices. When I use set analysis, I can get the results which I want but since my table is so long, and there are lots of months, I can't use set analysis by entering the dates by hand. Is there any easy way or better solution for that? 

Thanks in advance.

sum( {$<Year={2009}>} Sales )

My set analysis is, sum({$<Date={'02.01.2018'}>}price)-sum({$<Date={'01.01.2018'}>}price)

My table looks similar to this.

[jonathandienst]

What sort of output do you want - single value, table by some dimension(s). Are you looking for last date vs last date or month on month?

[emrekaya]

My purpose is to find the trend as a percentage then to show that in a chart. I am trying to find

(n+1th month-nth month)/nth month

I am looking for month on month.