Subtracting values from the same column but different rows in power bi - powerbi

Question

I'm calculating the difference of "closed column". All data is in one column and I'm calculating the difference between Row2-Row1 for all the rows. I'm getting results as some positive values and some negative. Positive values are coming correct but negative values are incorrect. I'm applying the formula
diff =
Table3[Value] -
CALCULATE(
SUM (Table3[Value]),
FILTER(
Table3,
Table3[Index] = EARLIER(Table3[Index])- 1
)
).
Screenshot of my formula
Output after applying formula, -ve and +ve values
Please help how can I correct my -ve values?
Month Week Month End Closed Open GT IN
01/2020 W01-2020 N 71 178 249 71
01/2020 W02-2020 N 284 189 473 213
01/2020 W03-2020 N 550 210 760 266
01/2020 W04-2020 N 861 185 1046 311
01/2020 W05-2020 Y 1185 205 1390 324
02/2020 W06-2020 N 370 206 576 370
02/2020 W07-2020 N 665 209 874 295

Answer 1

In Power Query Editor, I have added an Index column started from 1 to the data and the output is as below-
Now, create this below measure to get previous rows Closed value in the current row-
prev_row_closed_value =
CALCULATE(
SUM (your_table_name[Closed]),
FILTER(
ALL(your_table_name),
your_table_name[Index] = MIN(your_table_name[Index]) - 1
)
)
For calculating difference, use this below measure-
diff =
MIN(your_table_name[Closed]) -
CALCULATE(
SUM (your_table_name[Closed]),
FILTER(
ALL(your_table_name),
your_table_name[Index] = MIN(your_table_name[Index]) - 1
)
)
Here is output from the above measure-

Answer 2

In Dax you can use the following formulas.
In step one we create a column to get your Week Column in an order:
YearWeek = CONVERT(RIGHT(Sheet1[Week], 4) & MID(Sheet1[Week],2,2),INTEGER)
This is creating an integer value our of your year and month. Next we can use this to get the previous closed amount to be substracted where we filter first on the correct month. Be aware that I take the assumption this is a date column.
In =
var curMonth = Sheet1[Month]
var curYW = Sheet1[YearWeek]
var filterMonthYW = FILTER(Sheet1, curMonth = Sheet1[Month] && curYW > Sheet1[YearWeek])
var MaxYW = CALCULATE(MAX(Sheet1[YearWeek]), filterMonthYW)
return Sheet1[Closed] - CALCULATE(MAX(Sheet1[Closed]), FILTER(filterMonthYW, MaxYW = Sheet1[YearWeek] ))
Sheet1 is your table..
End result: