bugPSPP - Bugs: bug #18572, Warn if grouping variables are out...

 
 

bug #18572: Warn if grouping variables are out of order

Submitted by:  Ben Pfaff <blp>
Submitted on:  Thu 21 Dec 2006 11:22:35 PM UTC  
 
Category: OtherSeverity: 1 - Wishlist
Status: NoneAssigned to: Ben Pfaff <blp>
Open/Closed: OpenRelease: Future
Effort: 0.00

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Thu 21 Dec 2006 11:22:35 PM UTC, original submission:

It is a fairly common mistake, in my experience, to forget to sort data on the split variables when SPLIT FILE is in use, or to similarly forget to sort data on the group variables for RANK, and so on for other forms of grouping. At least, when I'm trying to use PSPP for tasks, I sometimes forget.

It would be nice if we could warn about this, so that users don't get too surprised, but it's somewhat difficult because we don't know the intended sort order. The actual sort order could be any permutation of the grouping variables, and each column could be in ascending or descending order. For N grouping variables there are 2*N N! sort orders, so a brute-force algorithm is going to be too slow. Also, we have to do it "online": we only get one pass through the data.

I have, however, figured out a decent algorithm that is both efficient and usually figures out when data is not sorted. At some point, I should implement this in PSPP. See http://groups.google.com/group/comp.programming/msg/c7ebefe24af2f930 for details.

Ben Pfaff <blp>
Project AdministratorIn charge of this item.

 

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    Follow 2 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sat 14 May 2011 04:39:18 AM UTCblpReleasePost-0.6.0=>Future
    Wed 25 Jul 2007 03:20:06 PM UTCblpReleaseNone=>Post-0.6.0

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