Re: CLEAR TRANSFORMATIONS ?

[John Darrington]

On Thu, Jul 05, 2007 at 09:27:12AM -0700, Ben Pfaff wrote:
     [Sorry, I fell off the net for a few days when my wife and I were
     moving from one house to another and our Internet service hadn't
     yet been transferred.  I will probably be sporadic for another
     couple of days.]

No worries.

     > You're right!  The manuals do have this example.  I tried running that
     > example on v15 and it does exactly what the manual says it won't do!!
     > It DOES NOT remove the INDEXQ variable! (see attached output file).
     
     I have one question first: in what way did you make SPSS run that
     syntax?  There is a distinction between "interactive" and "batch"
     environments made in the manual.  I see the documented behavior
     on a very old version of SPSS here: the variable is dropped in
     interactive mode, CLEAR TRANSFORMATIONS just yields a warning in
     batch mode.

I started the SPSS gui, opened a new syntax window, typed in the
syntax and activated the 'Run' menu.  I don't know whether that means
it's "interactive" or "batch" --- I suppose it must be batch.
     
     > So I suppose the question for us is, do we follow the manual or our
     > observations ?
     
     I can't see how this is anything but a bug in SPSS, so I would
     rather follow the documentation.

OK.
     
     > I can see that for optimisation reasons it's desireable not to execute
     > this transformation when running from a script, but the GUI needs to
     > run it, when it redraws the data sheet.  Otherwise the user will get
     > confused.   So maybe these "hidden" transformations should be
     > specially marked as such (perhaps in a seperate transformation chain)?
     
     Yes, I agree that they should be marked.  A separate
     transformation chain is a reasonable implementation choice, I
     think.
     
     I am not sure that the GUI really needs this, assuming that it
     runs something like proc_execute() before updating the data
     sheet.  If it does that, then any "hidden" transformations will
     be executed on the spot; if it doesn't, it seems like even an
     ordinary transformation like COMPUTE wouldn't update the data
     sheet whether it created a new variable or not.  So my guess is
     that it is important only for CLEAR TRANSFORMATIONS.

The PSPP gui, like you say, currently runs proc_execute() after
processing every syntax fragment.  But this is something that I'm
planning to change very shortly  --- it's not what Spss does, and it
means that the most powerfull uses of transformations are
inaccessible.  I'm planning to make the gui more in line with Spss:

When a transformation is active, it displays a "Transformation
Pending" sign in the status bar, and enables the "Run Pending
Transformations" menuitem, which when activates simply runs EXECUTE.

J'

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