I have three years 2020, 2019, 2018 each has a set of questions with corresponding responses :
2020 -> a has 10
2020-> b has 15
...
similarly,
2019-> a has value 20
2019-> b has value 25
...
2018 -> a has value 30
2018 -> b has value 35 where a,b,... are questions for that year.
Now the ask is to get the difference for value (2020.a) - value (2019. a), value(2020.b) - value(2019.b) and so on for all consecutive years
I don't want to hard code as in 2021 we would need 2021<->2020
