Calculating percentage change between last consecutive months

[carollyna205]

Month	A	B	C	D	E
January	58	123	123	234	23
February	64	234	233	44	34
March	34	455	333	56	56
April	55	333	456	77	78
Change

Hi, 

Let's say I have table like this. I am trying to add row at the en 'Change' which will show me precentage change between last 2 months, so basicaly formula (April-March)/March*100  how can I add this? Note that every month data will be refreshed and new row with new month will be added so I always want only change between current month and previous month % comparison. 

[tamerj1]

hi @carollyna205 

how does the source data look like? Are you utilizing a date table?

[carollyna205]

Each month I run Python script wchich adding data for current month, its basicly table with over 30k rows each month and each month that 3ok rows are added to previous file, so its one big file with 100k+ rows and aroung 40 columns. This visualisation is based on column Month and the columns A,B,C,D etc are columns for specific platforms. So at the end of May Python script will generate new data and row for May will show up and I would like to have always additional row on the end which calculate precetage of change between current month and previous month. If not possible to have it at the bottom of the table I dont mind having additional table with comparison only 

[tamerj1]

@carollyna205 

what date attributed columns do you have in your table?

[carollyna205]

Count of number of users - as values
Platform type - as columns

date format cell (month) - as rows

[tamerj1 · Accepted solution]

@carollyna205 

To play it safe (incase you have different years) it is better to have a YearMonth Calculated Column. 
YearMonth = FORMAT ( 'Table'[Date], "YYMM" )

then the measure for A for example would be

A Measure =
VAR Last2Months =
TOPN ( 2, VALUES ( 'Table'[YearMonth] ) )
VAR LastMonth =
MAXX ( Last2Months, 'Table'[YearMonth] )
VAR PenultimateMonth =
MINX ( Last2Months, 'Table'[YearMonth] )
VAR LastValue =
CALCULATE ( SUM ( 'Table'[A] ), 'Table'[YearMonth] = LastMonth )
VAR PenultimateValue =
CALCULATE ( SUM ( 'Table'[A] ), 'Table'[YearMonth] = PenultimateMonth )
RETURN
IF (
HASONEVALUE ( 'Table'[YearMonth] ),
SUM ( 'Table'[A] ),
FORMAT ( DIVIDE ( LastValue - PenultimateValue, PenultimateValue ), "Percent" )
)

[carollyna205]

Thank you, Overal it works but it using data from first 2 months instead of last 2 months, I know there is no BOTTOMN eqivalent to TOPN, do you have any idea how to solve this. I am new to PowerBi so still learning 

[carollyna205]

Actually I found solution for this, Thank you for help!

[tamerj1]

@carollyna205 

what date attributed columns do you have in your table?