How to Calculate Time difference from a single column

[Leslie1015]

Hello guys,

I'm new to power BI and I really need help in getting the time difference from a single column,

I have the Date and and Index. I needed an output like this. Can someone help me

			Time Difference
Date	Index
Wed, 01 Mar 2023 07:00:53	0
Wed, 01 Mar 2023 07:01:12	1		0:00:19
Wed, 01 Mar 2023 07:01:23	2		0:00:11
Wed, 01 Mar 2023 07:01:30	3		0:00:07
Wed, 01 Mar 2023 07:07:30	4		0:06:00
Wed, 01 Mar 2023 07:09:30	5		0:02:00

[ronrsnfld · Accepted solution]

In Power Query (Transform Data), you can

• you don't need the Index column
• if Date column not sorted ascending, then do so
• Add a "shifted date column" where the dates are shifted down one
• Subtract the "shifted column" from the date column
• Remove the "shifted column"

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCk9N0VEwMFTwTSxSMDIwMlYwMLcyMLAyNVaK1cEha2hlaIRP1givXmMD3LLmeGUtwbKxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type datetime}}),
    
    #"Add Shifted Date Column" = 
        Table.FromColumns(
            Table.ToColumns(#"Changed Type") & 
            {{null} & List.RemoveLastN(#"Changed Type"[Date],1)},
            type table[Date=datetime, Shifted Date=nullable datetime]),
    
    #"Add Time Difference Column" = Table.AddColumn(#"Add Shifted Date Column", "Time Difference", 
            each [Date] - [Shifted Date], type duration),
            
    #"Remove Shifted Date Column" = Table.RemoveColumns(#"Add Time Difference Column",{"Shifted Date"})
in
    #"Remove Shifted Date Column"

You could also do this with DAX, using a similar algorithm.

Again, the below assumes the DATE column is sorted ascending.

You select to add a column, with this DAX formula:

Time Diff = var SHIFT = OFFSET(-1,ALL('Table'[Date]))
            return if(SHIFT=0,BLANK(),'Table'[Date] - SHIFT)

[ToddChitt]

From what I understand, you want the time difference from the previous row.

It's not going to be pretty but it should work:

1) Looks like you have already done a SORT BY on Date and added the Index column. Good keep those, you are gong to need them.

2) DUPLICATE this query. Add a Custom Column named [New Index] and make it equal [index] - 1.

3) MERGE the two queries. Join on [Index] from the original table and [New Index] of the new table.

4) Expand the new table and grab only the Date.

You should now have one date/time and the previous date/time on one row. 

Do the match between the two.

FYI: If this is SQL, you should investigate WINDOW functions, particularly LAG and LEAD which allow you to find the row X number of rows behind (LAG) or x number of rows ahead (LEAD) of the current rwo. Plus anytime you can do something in SQL instead of Power Query, do it.