From richard_stahlhut at urmc.rochester.edu  Wed Aug 12 18:25:13 2009
From: richard_stahlhut at urmc.rochester.edu (richard_stahlhut at urmc.rochester.edu)
Date: Wed, 12 Aug 2009 18:25:13 +0200 (CEST)
Subject: [Rd] 10x slower merge in mac 2.9.1 vs. 2.9.0 (PR#13890)
Message-ID: <20090812162513.55224282EF4F@mail.pubhealth.ku.dk>

Full_Name: Rick Stahlhut
Version: 2.9.1
OS: os x 10.5.7
Submission from: (NULL) (128.151.71.23)


I upgraded to 2.9.1 today from 2.9.0.   I work with large CDC (center for
disease control) datasets and start, frequently, with a series of 23 large-ish
merges to create the final dataset I work on.  I do this each time because (a) R
is fast.  why not?   and b) the datasets occasionally get updated by CDC and
it's easier to swap in new files that way.

One such merge is two data.frames with 10 variables and 10,000 rows each.  The
command in question is:

temp = merge (demo.2,ph,by="seqn",all.x=TRUE)

in 2.9.0, this command took 3.3 seconds.
in 2.9.1, it took 35.8 seconds.

I have reverted back to 2.9.0.

Additional packages loaded are:

library(Hmisc)
library(alr3)
library(epicalc)
library(ggplot2)
library(lattice)
library(reshape)
library(survey)
library(car) 

thanks very much for all the effort.  R is wonderful.



[Rd] 10x slower merge in mac 2.9.1 vs. 2.9.0 (PR#13890)
richard_stahlhut at urmc.rochester.edu