[R] Ordered factors and DBMS

Timothy H. Keitt tklistaddr at keittlab.bio.sunysb.edu
Thu Oct 4 19:28:43 CEST 2001

Doug's suggestions of joining two tables or defining a new type are a 
good ones, although you would have to do some manual manipulations in 
raw SQL. There is a general need to be able to split compound R types 
across more than one SQL column. It may be possible with RPgSQL if you 
redefind rpgsql.format.values.factor and friends, but I haven't tried 
this myself. It is something to think about as we develop a more general 
db interface.


F. Tusell wrote:

>Is there any way of preserving order of ordered factors when storing a
>table in PostgreSQL?
>I have been  using PostgreSQL and the RPgSQL package  to store a large
>table with answers such  as "Strong disagreement", "Strong agreement",
>"Mild disagreement".  "Mild agreement".  When reading the  table, such
>answers are  turned into  factors, apparently in  reverse alphabetical
>order.  If I  reorder them  using ordered(factor,  levels=the  order I
>want), everything  is fine for the  session, but saving  the table and
>re-reading it reverts to the original order.
>I have  a vague  feeling of having  seen this  asked, but I  could not
>locate any  references. I looked  also B.D. Ripley's  "Using Databases
>with R", but this problem is not discussed.

Timothy H. Keitt
Department of Ecology and Evolution
State University of New York at Stony Brook
Stony Brook, New York 11794 USA
Phone: 631-632-1101, FAX: 631-632-7626

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