Re: NPAR TESTS

Michael Kiefte <[email protected]> writes:

> It's the ranks.  You can sort them on disk, but that's only half the battle.  
> You've got to go through the cases again and assign the ranks to the actual 
> observations.
>
> In the end, the RANK command has to be done first anyway.  After that's done, 
> the rest is trivial.

As I understand it, RANK is essentially a matter of making a copy
of the active file and sorting the copy, then adding a variable
to the active file that describes the resulting sort order.  If
so, then it's probably a matter of augmenting our sort
functionality.  This will take a little bit of work--I want to
refactor the sort procedure anyway--but it shouldn't be a huge
deal.

Is the Wilcoxon signed-rank statistic important?  It's probably
better to put it off until RANK is implemented.

> Another observation: this is from my manual under the FREQUENCIES comand:
> * Maximum 500 variables total per FREQUENCIES command. 
> * Maximum of 32,767 observed values over all variables.
>
> No such limitations are listed for RANK.  Is this an omission or can SPSS do 
> ranks on disk?

Wouldn't surprise me if they could.  It's basically a sort, and
external sorts are not difficult to write.  They probably just
reuse the code from SORT CASES, the same way I'm planning to do
for RANK.  It might take a little extra effort because you have
to do *two* sorts--the first to get the ranks and the second to
restore the same case ordering as in the active file--but
certainly doable.
-- 
"Long noun chains don't automatically imply security."
--Bruce Schneier