[R] Remove levels

Thu Jun 13 16:14:38 CEST 2013

If you've read the R Inferno section, you already know that
following my example with

> levels(DATA$UnitName_1)
[1] "lake"  "pond"  "river"
> DATA$UnitName_1 <- factor(DATA$UnitName_1)
> levels(DATA$UnitName_1)
[1] "pond"  "river"

removes the empty factor level.

-------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77840-4352

----Original Message-----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org] On Behalf Of David Carlson
Sent: Thursday, June 13, 2013 9:00 AM
To: 'Shane Carey'; r-help at r-project.org
Subject: Re: [R] Remove levels

Works fine for me. Too bad you didn't include actual data:

> set.seed(42)
> DATA <- data.frame(UnitName_1=factor(sample(c("lake", "pond",
"river"),
+         15, replace=TRUE)), Var=sample.int(100, 15))
> DATA
   UnitName_1 Var
1       river  95
2       river  97
3        lake  12
4       river  47
5        pond  54
6        pond  86
7       river  14
8        lake  92
9        pond  88
10      river   8
11       pond  99
12      river  35
13      river  80
14       lake  39
15       pond  72
> toBeRemoved1 <- which(DATA$UnitName_1=="lake")
> toBeRemoved1
[1]  3  8 14
> DATA <- DATA[-toBeRemoved1,]
> DATA
   UnitName_1 Var
1       river  95
2       river  97
4       river  47
5        pond  54
6        pond  86
7       river  14
9        pond  88
10      river   8
11       pond  99
12      river  35
13      river  80
15       pond  72

-------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org] On Behalf Of Shane Carey
Sent: Thursday, June 13, 2013 7:03 AM
To: r-help at r-project.org
Subject: [R] Remove levels

I have a dataframe consisting of factors in one column. Im trying to
remove
certain levels using the following code:
toBeRemoved1<-which(DATA$UnitName_1=="lake")
DATA<-DATA[-toBeRemoved1,]

However it will not remove the level "lake"

In the past this worked for me, but its not working now. Any help
appreciated.

Thanks

-- 
Shane

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