Re: [R] x[x$a=="q",,drop=TRUE]

From: Tae-Hoon Chung <thchung_at_tgen.org>
Date: Thu 02 Jun 2005 - 04:20:02 EST


Hi, Mikkel;

The problem here, I think, is that spray$PD is NOT recognized as character in R. Actually, R understands it as factors according to your printout. This happens quite a lot if you use read.table and come across characters within the data file. One remedy I use often use is doing something like

spray$PD <- as.character(spray$PD)

to make it sure that spray$PD is character.

Tae-Hoon Chung
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Tae-Hoon Chung

Post-Doctoral Researcher
Translational Genomics Research Institute (TGen) 445 N. 5th Street (Suite 530)
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On 6/1/05 11:08 AM, "Mikkel Grum" <mi2kelgrum@yahoo.com> wrote:

> 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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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jun 02 04:24:34 2005

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