R help - Feb 2003 - Data manipulation

I am interested in building a model with a subset of data from a column.

The first 6 lines of my data look like this:
    QUAD YEAR SITE TREAT HERB TILL PLANT SEED Kweed 
1     A4 2002    s     1    N    N     N    N 55.00   
2    A10 2002    s     1    N    N     N    N 60.00   
3     B2 2002    s     1    N    N     N    N 35.00  
4     C2 2002    s     1    N    N     N    N 23.00   
5     C9 2002    s     1    N    N     N    N 70.00   
6     11 2002    m     1    N    N     N    N 22.00   

I tried this command to get the subset I want:
> knap.fit1<-(lm(Kweed~TREAT[41:60,81:100,101:120,121:140], data=knap))
No luck.
 
Can anyone tell me how to code for this subset.

Thanks

Lew Stringer
M.S. Student- Land Rehabilitation
Dept. of Land Resources and Environmental Sciences 
Montana State University
822 Leon Johnson Hall
Bozeman, MT 59717
Lab:(406)994-6811
Fax:(406)994-3933

You might want to try subsetting the data frame first, and then fit the
model.  Something like

knap.sub <- knap[c(41:60,81:100,101:120,121:140), ]
knap.fit1 <- lm(Kweed ~ TREAT, data = knap.sub)

might work for you.

-roger
_______________________________
UCLA Department of Statistics
rpeng at stat.ucla.edu
http://www.stat.ucla.edu/~rpeng

On Fri, 7 Feb 2003, Lew wrote:
> I am interested in building a model with a subset of data from a column.
> 
> The first 6 lines of my data look like this:
>     QUAD YEAR SITE TREAT HERB TILL PLANT SEED Kweed 
> 1     A4 2002    s     1    N    N     N    N 55.00   
> 2    A10 2002    s     1    N    N     N    N 60.00   
> 3     B2 2002    s     1    N    N     N    N 35.00  
> 4     C2 2002    s     1    N    N     N    N 23.00   
> 5     C9 2002    s     1    N    N     N    N 70.00   
> 6     11 2002    m     1    N    N     N    N 22.00   
> 
> I tried this command to get the subset I want:
> 
> > knap.fit1<-(lm(Kweed~TREAT[41:60,81:100,101:120,121:140],
data=knap))
> No luck.
>  
> Can anyone tell me how to code for this subset.
> 
> Thanks
> 
> Lew Stringer
> M.S. Student- Land Rehabilitation
> Dept. of Land Resources and Environmental Sciences 
> Montana State University
> 822 Leon Johnson Hall
> Bozeman, MT 59717
> Lab:(406)994-6811
> Fax:(406)994-3933
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
>

Dear Lew,

You could use the subset argument to lm:

         knap.fit1 <- lm(Kweed ~ TREAT, data=knap, 
subset=c(41:60,81:100,101:120,121:140))

(You could alternatively subscript both Kweed and TREAT, rather than just 
TREAT, but this is unnecessarily complicated; as well, you'd need to use 
c() within the subscript, as in Kweed[c(41:60,81:100,101:120,121:140)].)

John

At 03:36 PM 2/7/2003 -0700, Lew wrote:
>I am interested in building a model with a subset of data from a column.
>
>The first 6 lines of my data look like this:
>     QUAD YEAR SITE TREAT HERB TILL PLANT SEED Kweed
>1     A4 2002    s     1    N    N     N    N 55.00
>2    A10 2002    s     1    N    N     N    N 60.00
>3     B2 2002    s     1    N    N     N    N 35.00
>4     C2 2002    s     1    N    N     N    N 23.00
>5     C9 2002    s     1    N    N     N    N 70.00
>6     11 2002    m     1    N    N     N    N 22.00
>
>I tried this command to get the subset I want:
>
> > knap.fit1<-(lm(Kweed~TREAT[41:60,81:100,101:120,121:140],
data=knap))
>No luck.
>
>Can anyone tell me how to code for this subset.
-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
-----------------------------------------------------