R help - Aug 2008 - stats tests on large tables

I have a large table of data which i can read in using read.table. 
I then want to conduct various tests on the data.

Is there a simple way to conduct these tests by specifying the column headers
which relate to different conditions of the experiment?

e.g. data1 <- read.table("test.table", header=TRUE)
t.test(test~control, data = data1)

Which doesn't work and results in the error
"Error in t.test.formula(test ~ control, data = data1) : 
  grouping factor must have exactly 2 levels"


Many Thanks

Richard
	[[alternative HTML version deleted]]

Try
t.test(data1[,1],data1[,2]) 
for the first two columns of data1.




--- On Tue, 8/26/08, Richard Emes <r.d.emes at hfac.keele.ac.uk> wrote:
> From: Richard Emes <r.d.emes at hfac.keele.ac.uk>
> Subject: [R] stats tests on large tables
> To: r-help at r-project.org
> Received: Tuesday, August 26, 2008, 11:52 AM
> I have a large table of data which i can read in using
> read.table. 
> I then want to conduct various tests on the data.
> 
> Is there a simple way to conduct these tests by specifying
> the column headers which relate to different conditions of
> the experiment?
> 
> e.g. data1 <- read.table("test.table",
> header=TRUE)
> t.test(test~control, data = data1)
> 
> Which doesn't work and results in the error
> "Error in t.test.formula(test ~ control, data = data1)
> : 
>   grouping factor must have exactly 2 levels"
> 
> 
> Many Thanks
> 
> Richard
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained,
> reproducible code.

      __________________________________________________________________
[[elided Yahoo spam]]

On 27/08/2008, at 3:52 AM, Richard Emes wrote:
> I have a large table of data which i can read in using read.table.
> I then want to conduct various tests on the data.
>
> Is there a simple way to conduct these tests by specifying the  
> column headers which relate to different conditions of the experiment?
>
> e.g. data1 <- read.table("test.table", header=TRUE)
> t.test(test~control, data = data1)
>
> Which doesn't work and results in the error
> "Error in t.test.formula(test ~ control, data = data1) :
>   grouping factor must have exactly 2 levels"
	with(data1,t.test(test ~ control)) # You do not need to specify the  
method explicitly.

		cheers,

			Rolf Turner

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