Previous month categorical value Power BI - powerbi

Question

I have the table which looks something like this. I am trying to find a way to find status change per an account, e.g. if the current month the status is Written off but it was Active last month, the tag should be Newly written Off. Is it feasible in Power BI? I found PREVIOUSMONTH but it deals only with measures, not categorical values like I have.

Answer 1

this seems like a trivial problem, but I found out, that it's not easily solvable in PowerBI.
Before showing the way I solve this, I would recommend you to solve it prior to loading data to PowerBI (ie. in the data source).
If that is not possible here's what you should do:
(recommended) Create T-1 data column == column, which has the previous date for comparison (for you, its previous month or date):
T-1 date =
VAR __acc_id = TABLE[account_id]
VAR __date = TABLE[date]
RETURN
CALCULATE(MAX(TABLE[date]),FILTER(ALL(TABLE), TABLE[account_id] = __acc_id && TABLE[date] < __date))
The filter part of calculation "returns" part of the table, which has the same account_id as current row and smaller date then current row. After that, we simply select the max date, which should be the previous one.
This way, we find the biggest previous date for each account.
If you know what the previous date is, feel free to skip this step.
Prior to the creation of the status column itself, I would create a calculated column, which contains the previous status. The column should be calculated like this:
t-1 status=
var __acc_id = TABLE[account_id]
var tdate = TABLE[T-1 date] //CREATED IN PREVIOUS STEP OR YOUR PREVIOUS DATE METRIC(LIKE dateadd or previousmonth function)
return
CALCULATE(firstnonblank(TABLE[status]), FILTER(ALL(TABLE), TABLE[account_id]=__acc_id && table[date] = tdate))`
With the previous status column, we now have the current and previous status columns, which should be enough to correctly label the "rows" with simple if statement.
The calculated column formula might look something like this:
status_label = if(TABLE[status] == "Written off" && TABLE[t-1 status] == "active", "newly written off", "something else").
If simple IF isn't enough, have a look at switch statement
This sequence of steps should solve your issue, but I have to admit, it's not performance efficient. It would be better to solve it in PowerQuery, but sadly, I do not know how. Any solution using PowerQuery would be highly appreciated.