Start and end time

[jojo54]

Hi there, pretty new to Power BI.  I'm trying to replicate something I do in Excel in Power BI, mainly because excel can't handle the amount of data that's being processed.

I'm trying to figure out how full a cafe is in different parts of the day.  I have the following data about each customer and what time they arrive and leave the cafe.

Name	Entry Time	Exit Time
Person 1	6:00	9:00
Person 2	7:00	8:30
Person 3	8:00	9:15
Person 4	6:45	10:00
Person 5	7:15	7:45

And I want to see how many people are actually in the cafe at any one point in time, so like the below

	6:00	6:15	6:30	6:45	7:00	7:15	7:30	7:45	8:00
Person 1	1	1	1	1	1	1	1	1	1
Person 2					1	1	1	1	1
Person 3
Person 4				1	1	1	1	1	1
Person 5						1	1	1
Total	1	1	1	2	3	4	4	4	3

I can definitely do it in excel but I can't figure out how to get it done in Power BI! Any help would be great!

[mussaenda]

Hi @jojo54 ,

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCkgtKs7PUzBU0lEyszIwAFKWICpWBy5lBBQzh0hZWBmjSBmDxaC6DE2RpUzABpqYAilDAzQTTcEmGkIooJLYWAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Name = _t, #"Entry Time" = _t, #"Exit Time" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Name", type text}, {"Entry Time", type time}, {"Exit Time", type time}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each List.Times([Entry Time], 20, #duration(0, 0, 15, 0))),
    #"Expanded Custom" = Table.ExpandListColumn(#"Added Custom", "Custom"),
    #"Changed Type1" = Table.TransformColumnTypes(#"Expanded Custom",{{"Custom", type time}}),
    #"Added Custom1" = Table.AddColumn(#"Changed Type1", "Custom.1", each if [Exit Time] < [Custom] then "Hide" else "Show"),
    #"Filtered Rows" = Table.SelectRows(#"Added Custom1", each ([Custom.1] = "Show"))
in
    #"Filtered Rows"

From the result you posted, The person 3 must also have count in 8:00 time because 8:00 is his entry time, right?

File is here

[wynhopkins]

Nice approach @mussaenda ,   why use the 20 in List.Times?

Also, @jojo54 ,  given this code will work in Excel I'd be interested to know what performance issues your having that you're trying PowerBI.   Is it the 32 Bit Excel version that's limiting you?

Wyn

[mussaenda]

Hi @wynhopkins,

Thank you fo the compliment. I just used 20 because I assumed that a person stays in a cafe max like 5 hours.

20 can be changed, @jojo54 .  depends on your need. 🙂

Have a nice day!

[Geradav]

Hi @jojo54 

Here is an alternative using DAX

Number of clients =
VAR vMinVal =
    MIN ( TimeTable[Value] )
VAR vMaxVal =
    MAX ( TimeTable[Value] )
VAR vClientEntry =
    CALCULATE (
        COUNTROWS ( ClientsTbl ),
        TimeTable[Value] <= vMinVal,
        ALL ( TimeTable )
    )
VAR vClientExit =
    CALCULATE (
        COUNTROWS ( ClientsTbl ),
        TimeTable[Value] >= vMaxVal,
        ALL ( TimeTable ),
        USERELATIONSHIP ( ClientsTbl[Exit Time], TimeTable[Value] )
    )
RETURN
    MIN ( vClientExit, vClientEntry )

Create a time table, then create a relationship between Start Time and the time value, and a second one between Exit Time and the time value. One will be an active relationship, while the second will be inactive.

Like this:

Then you can use that measure in your visualization. Time value in X axis and the measure in the Value area

And you can also make use of the same DAX code in the data model of Excel (Power Pivot)

Let us know what works for you

[mussaenda]

Hi @Geradav ,

Nice approach using dax! Is there a way to make the interval evey 15mins instead of every 5mins?

[Geradav]

Hi @mussaenda 

I used a table function to generate a time series with an increment of 5 minutes, so yes, it can easily be changed to 15 minutes.

TimeTable =
GENERATESERIES ( TIME ( 5, 0, 0 ), TIME ( 13, 0, 0 ), TIME ( 0, 15, 0 ) )

[jojo54]

Thanks all! Apologies for late reply - going to take a look and give these solutions a go!

[jojo54]

I have ~3m lines of data so excel is extremely limiting! I'm looking at it across every day, across a few years

[jojo54]

@Geradav 

Thanks for this solution!  I like that I can actually write this down to work out what it's doing!

But I'm finding an issue with the below: (updated table)

Name	Entry Time	Exit Time
Person 1	6:00	9:00
Person 2	7:00	8:30
Person 3	8:15	9:15
Person 4	6:45	10:00
Person 5	7:15	7:45

If I were to look at 8am, according to the DAX query,

vcliententry = 4

vclientexit = 4

So query will return 4 being min (4,4)

However there's actually only 3 people who's at the cafe (Person 1,2,4)

I tried writing this on paper and I've worked out that this mis-calculation occurs when there are people on the list who have exited prior to the TimeValue AND there are people who not yet entered into the cafe at the TimeValue.

Any ideas on how to fix this?

Thanks!

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