Re: CLEAR TRANSFORMATIONS ?

[Ben Pfaff]

John Darrington <address@hidden> writes:

> On Sat, Jun 30, 2007 at 07:55:27AM -0700, Ben Pfaff wrote:
>      There are a few subtleties I think.  First, I don't think we save
>      a copy of the dictionary that corresponds to the active file.
>      We'd need to do so, and then restore it for CLEAR
>      TRANSFORMATIONS.
>
> Spss doesn't do this.  So neither should we (at least not by default).

I think that SPSS does do this.  The SPSS 13, 14, and 15 manuals
all have an identical example that shows a data file being read,
some transformations being done on it, and then running CLEAR
TRANSFORMATIONS.  The text then states that the variables created
by the transformations no longer exist, because they were created
by transformations that have been discarded.

>      Second, some transformations are not exposed to the user and
>      should not be cleared.  The specific one I have in mind is the
>      DESCRIPTIVES transformation that produces Z scores.  As far as
>      the user is concerned that transformation doesn't exist so it
>      shouldn't be cleared.
>
> Is this really an issue?  These transformations only come into
> existance after the command has been called, and are destroyed before
> it terminates, so there's no possibility that CLEAR TRANSFORMATIONS
> can affect this.

The transformation that I'm talking about does persist after the
command terminates.  Take a look at cmd_descriptives and where
the call to setup_z_trns is located.
-- 
Ben Pfaff 
http://benpfaff.org