runs.test in by() statement

Thanks to Patric and Christian for swift and accurate help

I still had to learn the differnce between calling a function and
passing a call to a function. I had to coerce the first variable to be
a function but then it worked.

by(as.factor(exampledata$var), exampledata$interviewer, runs.test)

Regards
Christiaan

exampledata<-data.frame(interviewer=rep(letters[1:2], 1),
var=round(var=runif(40)))

I do the runs test on "var" and it works
runs.test(as.factor(exampledata$var))

I can catagorise the data by "interviewer" and get means using the by()
statement and that works perfectly
by(exampledata$var, exampledata$interviewer, mean)

Why is it impossible to use runs.test() as the function in the by()
statement instead of mean
 by(exampledata, exampledata$interviewer,
runs.test(as.factor(exampledata$var)))
 Error in FUN(X[[1L]], ...) : could not find function "FUN"

thanks
Christiaan

I always have trouble with "by" myself. I don't usually get an answer  
as quickly as I did here. I usually give up and move to "aggregate" or  
"ave".

First I limited the data given to "by" in the first argument to just  
the variable under question. Then by the time R sends the information  
to your function it may not be named what it was in the global  
environment, so I packaged those two functions "runs.test" and  
"as.factor" inside a packaging function that converted its name to  
"x". Seems to give possibly sensible results. See if this works for you.

 > by(exampledata$var, exampledata$interviewer,
               function(x) {runs.test(as.factor(x))} )
exampledata$interviewer: a

	Runs Test

data:  as.factor(x)
Standard Normal = -0.8823, p-value = 0.3776
alternative hypothesis: two.sided

----------------------------------------------------------------------------------------------
exampledata$interviewer: b

	Runs Test

data:  as.factor(x)
Standard Normal = 0, p-value = 1
alternative hypothesis: two.sided

David Winsemius


On Jan 14, 2009, at 3:13 AM, christiaan pauw wrote:

> by(exampledata, exampledata$interviewer,
> runs.test(as.factor(exampledata$var)))