Using PowerPivot in Excel 2013 - Business Intelligence in Microsoft SharePoint 2013 - page 116

To upgrade the 2010 workbook to work in Excel 2013 by using the Data Model, you need to use
the PowerPivot Add-in. This is covered in the next section. Okay, there's nothing alarming about the
message. You get a similar message when opening a PowerPivot v1 workbook in a PowerPivot v2
environment. However, the message is misleading because the data is not upgraded after you click
OK to dismiss the dialog. Click Refresh again; the message reappears. What is going on? It's nothing
more than Excel displaying an inappropriate message in the current context—an issue that should
be fixed. If you have PowerPivot installed and click Manage on the PowerPivot tab, Excel displays the
message in Figure 4-26, but this time after you click OK, you see the confirmation message shown
in Figure 4-27. The difference now is that although Excel displays the same message as the refresh
attempt, the message is shown in a context in which the update can be done.
FIGURE 4-27 The unsupported data update confirmation message box.
And now, after clicking OK, the data is truly updated. The message that Excel displays when you
attempt to refresh the incompatible workbook should be more instructive.
Calculations with DAX
DAX formulas are designed to be as similar as possible to Excel formulas. Just as in Excel, all DAX
formulas begin with an assignment operator, such as an equals sign ( = ), but DAX works with tables (as
in a database) rather than with cells arranged in a tabular fashion. The main difference between Excel
formulas and DAX formulas is that DAX never uses cell coordinates (B2, C3, and so on). Also, DAX
does not work with cell ranges. To work with ranges, you can use DAX functions to apply filters to
narrow down the data to that in which you're interested.
Here is a simple example of a DAX formula:
=FactInternetSales[SalesAmount]-FactInternetSales[TotalProductCost]
This calculation defines the Margin column in the sample workbook by subtracting the
TotaProductlCost column from the SalesAmount column, which yields a profit-margin value.