[R] how to iterate

[Greg Snow]

Here is one approach:

> tmp <- scan()
1: 1 127 1 261 1 142 1 183 1 234 1 162 2 173 2 321 2 168 2
20: 197 2 213 2 261 3 198 3 126 3 167 3 154 3 134 3 187 3 109 3 210
41: 
Read 40 items
> my.df <- as.data.frame( matrix(tmp, ncol=2, byrow=TRUE) )
> names(my.df) <- c('Category','Variable')
> 
> my.df$Category <- factor(my.df$Category)
> 
> fit1 <- aov( Variable ~ Category, data=my.df )
> summary(fit1)
            Df Sum Sq Mean Sq F value  Pr(>F)  
Category     2  13005    6503  2.7324 0.09355 .
Residuals   17  40456    2380                  
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 
> 
> out1 <- replicate(99, summary(aov( sample(Variable) ~ Category,
data=my.df ) ) )
> 
> 
> # now look at a histogram of the p-values
> tmp <- sapply( out1, function(x) x['Pr(>F)'][1,1] )
> hist(tmp)
> 

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at intermountainmail.org
(801) 408-8111
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Tavpritesh Sethi
> Sent: Tuesday, June 26, 2007 8:08 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] how to iterate
> 
> for the following example dataset:-
>    Category Variable 1 127 1 261 1 142 1 183 1 234 1 162 2 
> 173 2 321 2 168 2
> 197 2 213 2 261 3 198 3 126 3 167 3 154 3 134 3 187 3 109 3 
> 210 I have performed Anova on the measured variable 
> (column#2) for the groups
> 1,2&3 (column#1). Now I want to randomize the values in C#2 
> and reperform the test, say, a hundred times. Please suggest 
> a way for this iteration. The loop I tried to write didn't work.
> Thanks.
> 
> 	[[alternative HTML version deleted]]
> 
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