[R] parts of data frames: subset vs. [-c()]

[Stefan Th. Gries]

Dear all

I have a problem with splitting up a data frame called ReVerb:

» str(ReVerb)
`data.frame':   92713 obs. of  16 variables:
 $ CHILD    : Factor w/ 7 levels "ABE","ADA","EVE",..: 1 1 1 1 1 1 1 1 1 1 ...
 $ AGE      : Factor w/ 484 levels "1;06.00","1;06.16",..: 43 43 43 99 99 99 99 99 99 99 ...
 $ AGE_Q    : num  2.0 2.0 2.0 2.4 2.4 ...
 $ INTERVALS: num  2 2 2 2.25 2.25 2.25 2.25 2.25 2.25 2.25 ...
 $ RND      : int  34368 38311 14949 20586 72516 27186 88019 10767 114448 86146 ...
 $ SYNTAX   : Factor w/ 17 levels "Acmp","Amats",..: 15 12 8 15 7 16 7 7 16 7 ...
 $ LEXICAL  : Factor w/ 1643 levels "$ACHE","$ACT",..: 194 803 803 294 299 803 1562 299 679 1562 ...
 $ MORPH    : Factor w/ 337 levels "$","$ =inf","$ =prs",..: 9 20 9 39 184 231 57 67 231 39 ...
 $ COMPLEM  : Factor w/ 1989 levels "$","$ V PR=Lp [1.2]",..: 203 547 220 203 1101 368 1834 1667 368 1834 ...
 $ MATRIX   : Factor w/ 906 levels "$ ???","$ be PR=Aen",..: 5 5 5 308 5 856 5 5 856 308 ...
 $ SITUATION: Factor w/ 9 levels "[imitation of Mom: you know what I said]",..: 2 2 2 2 2 2 2 2 2 2 ...
 $ V_ANN    : int  1 1 1 4 4 4 4 3 3 3 ...
 $ QUEST    : int  0 0 0 0 0 0 0 0 0 0 ...
 $ EXCL     : int  0 0 0 1 1 1 1 0 0 0 ...
 $ U_LEN    : int  3 4 5 13 13 13 13 8 8 8 ...
 $ UTTERANCE: Factor w/ 55113 levels "","# (be)cause he wanted to .",..: 5696 39091 52180 2262 2262 2262 2262 3593 3593 3593 ...

The level causing the problem is SYNTAX:

» as.data.frame(sort(table(SYNTAX)))
              sort(table(SYNTAX))
Particles                     100
PR=N1                         144
Amats                         271
Trans_PR=A2                   787
Ditrans                      1181
Intrans_PR=A1                1399
Acmp                         2402
Trans_PR=V2                  2433
CPcmps                       2769
Vpreps                       4896
Intrans_V0                   5182
Trans_PR=L2                  7653
Trans_V02                    8117
Intrans_PR=L1                8457
Intrans_V1                   9643
Intrans_PR=V1               14987
Trans_V12                   22288


I would like to extract all cases where SYNTAX=="Ditrans" from ReVerb, store that in a file, and then generate ReVerb again without these cases and factor levels. My problem is probably obvious from the following lines of code:

» ditrans<-which(SYNTAX=="Ditrans")
» ReVerb1<-ReVerb[-c(ditrans),]; dim(ReVerb1)
[1] 91532    16
» 
» # ok, so the 92713-91532=1181 cases where SYNTAX=="Ditrans" have been removed, but ...
» 
» ReVerb1<-subset(ReVerb, SYNTAX!="Ditrans"); dim(ReVerb1)
[1] 91528    16
» 
» # ... so why don't I get 91532 again as the number of rows?
» 
Any ideas??

» R.version # on Windows XP with service Pack 2
         _              
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    2              
minor    1.1            
year     2005           
month    06             
day      20             
language R              

Thanks a lot,
STG
--
Stefan Th. Gries
----------------------------------------
Max Planck Inst. for Evol. Anthropology
http://people.freenet.de/Stefan_Th_Gries
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