R help - Dec 2003 - how to use apply on a two variable t-test

does anyone know how to use the apply function on a two-variable t-test? 
i've tried everything.

apply(data[1:4],1,t.test) # works, but only a one-variable test
apply((data[1:4],data[5:9]),1,t.test) # returns a syntax error

i've also tried using the for loop:

for (i in 1:1000) t.test(data[i,1:4],data[i,5:9])

doesn't print anything!  it processes for awhile, so i know it's doing 
the calculations.

t.test(data[1,1:4],data[1,5:9])

works fine! prints to the screen as i'd expect.

i have checked and double checked that sink() is empty.  please also 
send your reply to jbdunsmo at utmb.edu.  i receive the digest version of 
the mailing list.

thanks for any help,
jason

On 12/31/03 09:12, Jason Dunsmore wrote:
>does anyone know how to use the apply function on a two-variable t-test?
>i've tried everything.
Suppose d1 and d2 are data frames, and you want to do a t test of
column 1 of d1 vs. column 1 of d2, column 2 of d1 vs. column 2 of
d2, and so on.  Then

mapply(t.test,d1,d2)

will do it.  It wasn't clear from your orignal statement what
form your data were in.  You have to put them in a data frame for
this approach to work.

Jon
-- 
Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page:            http://www.sas.upenn.edu/~baron
R page:               http://finzi.psych.upenn.edu/ [down right now]

For your main question, see ?mapply.

For the "what happened to the output in my for loop"
FAQ: you need to put in an explicit print() around
the t.test call. At the command prompt, expressions are
evaluated and printed; elsewhere they are only
evaluated.

HTH and Happy New Year to all,
Simon
> -----Original Message-----
> From: Jason Dunsmore [mailto:jbdunsmo at utmb.edu]
> Sent: 31 December 2003 15:13
> To: r-help at stat.math.ethz.ch
> Subject: [R] how to use apply on a two variable t-test
> 
> 
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>  
> does anyone know how to use the apply function on a 
> two-variable t-test? 
> i've tried everything.
> 
> apply(data[1:4],1,t.test) # works, but only a one-variable test
> apply((data[1:4],data[5:9]),1,t.test) # returns a syntax error
> 
> i've also tried using the for loop:
> 
> for (i in 1:1000) t.test(data[i,1:4],data[i,5:9])
> 
> doesn't print anything!  it processes for awhile, so i know 
> it's doing 
> the calculations.
> 
> t.test(data[1,1:4],data[1,5:9])
> 
> works fine! prints to the screen as i'd expect.
> 
> i have checked and double checked that sink() is empty.  please also 
> send your reply to jbdunsmo at utmb.edu.  i receive the digest 
> version of 
> the mailing list.
> 
> thanks for any help,
> jason
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>  
 
Simon Fear 
Senior Statistician 
Syne qua non Ltd 
Tel: +44 (0) 1379 644449 
Fax: +44 (0) 1379 644445 
email: Simon.Fear at synequanon.com 
web: http://www.synequanon.com 
  
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