[Babase] Interpolation (MEMBERS) changes

Karl O. Pinc babase@www.eco.princeton.edu
Sun, 03 Apr 2005 18:11:39 +0000


After conversations with Susan I'm changing the way
interplation works.  (Both because I think we want
it changed and because the old foxpro based code is
too complicated and slow.)  I'll write later and post the
relevant section of the documentation at some point
before I wrap this up.  But I wanted to get this
out there so people could comment if anybody sees
a problem.

The changes are:

1) The BIOGRAPH.Statdate will no longer act like
a census, placing the individual in a group on
MEMBERS and interplating (backward in time) from
that date.  (Birth will continue to act "as a
census" and birthdays will continue to (sometimes)
have a MEMBERS.Origin of I and a MEMBERS.Interp
of 0.)

2) There will be a row on MEMBERS for an individual
for every day between the individual's Birth and
Statdate.  Interpolation will continue to place
the individual in his censused group for 14 days
on either side of the census, and after that the
individual will be in the unknown group.  (Group
9).

I think we have treated Statdates as 'census dates'
so that we would always have a MEMBERS row for
the individual's death date.  With the new
scheme we will have a row in MEMBERS for the
individual's death (or disappearance) date
but when the interval is too long beteween the
last census and the statdate the individual will
wind up in the unknown group on his death date
rather than the group last censused.

So, we'll see a lot more Unknown group memberships
in MEMBERS, with Origin of I.  I'm thinking that the Interp value
for these rows will continue to "count up"
from the nearest (in time) census that places the
individual in a group, unless the nearest
census (in time) both before and after are
'old style' non-interpolating rows.  In which
case the MEMBERS.Interp value will be 0.
(I think that the science folks think that
this will never happen, but I'm not so sure
about the data.  If it does show up and is
not supposed to, then we can fix the data.)


Karl <kop@meme.com>
Free Software:  "You don't pay back, you pay forward."
                 -- Robert A. Heinlein