the argument drop =TRUE is not meant to do that (see several responses from
Peter Dalgaard about this issue i.e.
http://finzi.psych.upenn.edu/R/Rhelp02a/archive/37333.html)
If you want to drop unused factor levels try:
sprayS$PD<-factor(sprayS$PD)
Cheers
Francisco
From: Mikkel Grum <[EMAIL PROTECTED]>
To: RHelp <[email protected]>
Subject: [R] x[x$a=="q",,drop=TRUE]
Date: Wed, 1 Jun 2005 11:08:46 -0700 (PDT)
I'm trying to select a subset of a dataframe while
dropping some factors. While the dataset gets smaller
all Factor levels remain and I need to get rid of
them. Strangely enough, I am almost certain that the
same code on the same data worked OK earlier today -
and it is not the first time that I'm not able to
replicate earlier results with this command (I know, I
might just be going crazy). What am I doing wrong?
I'm working on Windows Server 2003, R 2.1.0
(2005-04-18).
> str(spray)
`data.frame': 370 obs. of 7 variables:
$ PD : Factor w/ 8 levels
"Botrytis","Downy",..: 2 2 2 2 4 2 2 5 5 5 ...
$ postSpmtsQ: num 1309 1309 384 384 1044 ...
$ ante62Q : num 284 284 218 218 366 ...
$ ante08Q : num 331 331 228 228 492 ...
$ ante29Q : num 297 297 1067 1067 1034 ...
$ ante16Q : num 0 0 0.2 0.2 0 0 0 6.7 0 31.5 ...
$ Trt : Factor w/ 41 levels "Acrobat MZ WP",..:
27 5 27 5 36 27 5 24 24 24 ...
> sprayS <- spray[spray$PD == "Spidermites", , drop =
TRUE]
> str(sprayS)
`data.frame': 111 obs. of 7 variables:
$ PD : Factor w/ 8 levels
"Botrytis","Downy",..: 5 5 5 5 5 5 5 5 5 5 ...
$ postSpmtsQ: num 13395 31588 84254 136 619 ...
$ ante62Q : num 1357 21187 21819 218 237 ...
$ ante08Q : num 973 21740 25112 228 134 ...
$ ante29Q : num 2103 106970 66676 1067 119
...
$ ante16Q : num 6.7 0 31.5 0.2 0 0 0 0 14.3 0 ...
$ Trt : Factor w/ 41 levels "Acrobat MZ WP",..:
24 24 24 24 24 24 24 24 24 24 ...
> table(sprayS$Trt)
Acrobat MZ WP Agrifos Apollo 50 SC
CALMAG
0 0 13
0
DM-31 Dynamec 1.8 EC Equation Pro DF
Evisect S
0 13 0
0
Flint Floramite Impulse
Karate
0 15 0
0
Karate zeon Melody Meltatox 40 EC
MKP
0 0 0
0
Molasses Nembicidine Nimrod 250 EC
Nissorun 10 EC
0 0 0
12
Oberon Orthene 75 WP Oscar 20 SC
Pegasus
15 0 9
26
Polar 50 WSG Potfos Proplant
Pyrus
0 0 0
0
Ridomil MZ 63 5WP Rovral aqua flo Score 250 EC
Secure 36 SC
0 0 0
8
Sequestrone Shavit f Sporekill
Stroby 50 WG
0 0 0
0
Switch Tracer Trafos K
Vandozeb
0 0 0
0
Vitomex
0
cheers,
Mikkel
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