create interacion term using the VL commands suite

[Luis Pecht]

Hi,

I am trying to create interacion term using VL suite.

. webuse auto
(1978 automobile data)

. vl set

-------------------------------------------------------------------------------
                  |                      Macro's contents
                  |------------------------------------------------------------
Macro             |  # Vars   Description
------------------+------------------------------------------------------------
System            |
  $vlcategorical  |       2   categorical variables
  $vlcontinuous   |       2   continuous variables
  $vluncertain    |       7   perhaps continuous, perhaps categorical variables
  $vlother        |       0   all missing or constant variables
-------------------------------------------------------------------------------

I did it using a local macro:

. local covars0 $vlcontinuous i.($vlcategorical) (c.($vlcontinuous) i.($vlcategorical))##(c.($vlcontinuous) i.($vlcategorical))

. di "`covars0'"
headroom gear_ratio i.(rep78 foreign) (c.(headroom gear_ratio) i.(rep78 foreign))##(c.(headroom gear_ratio) i.(rep78 foreign))

however I was not able to do it using VL commands:

. vl substitute covars1 = i.vlcategorical##c.vlcontinuous

. vl dir

-------------------------------------------------------------------------------
                  |                      Macro's contents
                  |------------------------------------------------------------
Macro             |  # Vars   Description
------------------+------------------------------------------------------------
System            |
  $vlcategorical  |       2   categorical variables
  $vlcontinuous   |       2   continuous variables
  $vluncertain    |       7   perhaps continuous, perhaps categorical variables
  $vlother        |       0   all missing or constant variables
-------------------------------------------------------------------------------

. vl create vlcont = vlcontinuous
note: $vlcont initialized with 2 variables.

. vl create vlfv = vlcategorical
note: $vlfv initialized with 2 variables.

. vl dir

-------------------------------------------------------------------------------
                  |                      Macro's contents
                  |------------------------------------------------------------
Macro             |  # Vars   Description
------------------+------------------------------------------------------------
System            |
  $vlcategorical  |       2   categorical variables
  $vlcontinuous   |       2   continuous variables
  $vluncertain    |       7   perhaps continuous, perhaps categorical variables
  $vlother        |       0   all missing or constant variables
User              |
  $vlcont         |       2   variables
  $vlfv           |       2   variables
  $covars1        |           factor-variable list
-------------------------------------------------------------------------------

. vl substitute covars2 = i.vlfv##c.vlcont

. vl dir

-------------------------------------------------------------------------------
                  |                      Macro's contents
                  |------------------------------------------------------------
Macro             |  # Vars   Description
------------------+------------------------------------------------------------
System            |
  $vlcategorical  |       2   categorical variables
  $vlcontinuous   |       2   continuous variables
  $vluncertain    |       7   perhaps continuous, perhaps categorical variables
  $vlother        |       0   all missing or constant variables
User              |
  $vlcont         |       2   variables
  $vlfv           |       2   variables
  $covars1        |           factor-variable list
  $covars2        |           factor-variable list
-------------------------------------------------------------------------------

any clue ?? thanks