DAX Formula to Calculate Average Days Between Invoices

Objective

To calculate the average number of days between multiple invoices based on their corresponding dates stored in a dataset.

Formula

The following DAX formula calculates the average days between consecutive invoice dates:

AverageDaysBetweenInvoices = 
VAR InvoiceDates = 
    ADDCOLUMNS(
        'Invoices', 
        "NextDate", 
        LEAD('Invoices'[InvoiceDate], 1)
    )
RETURN 
    AVERAGEX(
        FILTER(
            InvoiceDates, 
            NOT(ISBLANK([NextDate]))
        ), 
        DATEDIFF(InvoiceDates[InvoiceDate], InvoiceDates[NextDate], DAY)
    )

Explanation of the Formula

1. ADDCOLUMNS Function:

   • This function is utilized to create a new table called InvoiceDates, which includes a calculated column named NextDate. This column holds the date of the next invoice using the LEAD function, which fetches the date of the subsequent invoice in a row sequence.

2. LEAD Function:

   • It retrieves the next invoice date by offsetting the current date by one row. This allows for the calculation of the time difference between consecutive invoices.

3. FILTER Function:

   • The FILTER function is employed to exclude any rows where NextDate is blank, ensuring that only valid date pairs are considered in the average calculation.

4. DATEDIFF Function:

   • This function calculates the difference in days between the current invoice date and the next invoice date.

5. AVERAGEX Function:

   • Finally, AVERAGEX computes the average of the day differences calculated over the filtered table.

Practical Example

Assume you have the following dataset, Invoices, with two columns:

Using the provided DAX formula, the calculation will be as follows:

• Days between Invoice 1 and 2: 9 days
• Days between Invoice 2 and 3: 10 days
• Days between Invoice 3 and 4: 5 days
• Days between Invoice 4 and 5: 7 days

Thus, the average would be calculated as:

[ \text{Average} = \frac{9 + 10 + 5 + 7}{4} = 7.75 \text{ days} ]

Conclusion

The provided DAX formula effectively computes the average number of days between consecutive invoices using the specified invoice dates. This formula can be further tailored to meet specific needs or dataset structures.

For more advanced DAX techniques and data analysis insights, consider exploring resources available on the Enterprise DNA Platform.