Using time in expressions

[Anonymous]

Heyy guys

I am not quite good in using Qlikview, I understand most basic things and the scripts and everything are already loaded so I don't have to change things there.

Anyway on to the question: I need to make a graph of the increase/decrease in sales regarding the previous month. Note that first off all, the data is not updated, so I want to do it with the data I have in the database, which ends on 24/04/2017. This can be updated.

So far a variable has been made to store this data using the max function. This means that if the database is updated, the date can change to let's say 25 Mai or 1 June etc.

What should the expression do exactly: If I click a month, I want the chart (bar) to show me the increase or decrease compared to the previous month. So the expression should be made in such way that it knows that the last month will be March 2017 (since April is not a full month in the set) and then it should compare it to Feb 2017 (so (Mar 2017 - Feb 2017)/Feb 2017). If I click March and February, the expression should be made that the bar chart shows me 2 lines: the february line, comparing jan and feb and the march line, comparing feb and march. I do not want to make variables 'storing' feb and march because first off all: changing the current selections won't work anymore then, second: if the data is updated, the last full month should change to April or even Mai, depending on how much data is loaded in the database.

Thanks in advance for the help and please, explain as if you are talking to a real newbie because that's what I am