By the end of this chapter you will be able to:

• Create macros
• Use macros

Creating macros

Macros are used to create reusable expressions. They can be thought of as, the ability to write bespoke functions. Macros can optionally take in a number of parameters to use within its expression:  

1. Find

   Insert excerpt
   _macros _macros nopanel true

    in the repository
2. Right-click and select

1. Insert excerpt
   _addIcon _addIcon nopanel true

    Add Macro
2. Configure the macro:
   1. Name: NumOfWeeks
   2. Minimum Parameters: 2
   3. Maximum Parameters: 2
   4. Expression: create an expression to work out the number of weeks - as a whole number – between two dates

      1. Use the

1. 1. 1. functions dateDiff() and round() to help with this

1. 1. 1. Expand
         title See Completed Expression
         do(      // Create variables from incoming parameters      $Date1 = $args[1],      $Date2 = $args[2],      // Get the difference in time between the two dates      $dateDiffMilliSecs = dateDiff( $Date2, $Date1 ),      // Round the answer into whole weeks      round($dateDiffMilliSecs/(1000*60*60*24*7), 0 )      )

         
         

2. Press 

   Insert excerpt
   _finish _finish nopanel true

    to save your new macro

Using Macros

1. Create a new model: Try Macros
2. Drag the

1. table MC Macro Terminated Customers on to your model
   1. This contains some key dates for terminated customers: the signup date; the date that the customer terminated their service; the date that the final debt on the customer's account was cleared
   2. Add

1. 1. Insert excerpt
      _attributes _attributes nopanel true

       for:
      1. the number of weeks between signup and termination
      2. the number of weeks between termination and the final debt being cleared

   2. In each case, use your macro to calculate the number of weeks between the two dates

      Expand
      title

1. 1. How?

      Expression: NumOfWeeks(_out.SIGNUP_DATE,_out.TERMINATION_DATE) Expression: NumOfWeeks(_out.TERMINATION_DATE,_out.DEBT_CLEARED)

      
      

2. Run the table MC Macro Terminated Customers to test your new attributes