[R] self-written function

[Petr Pikal]

Hi Christoph

On 28 Jan 2005 at 11:04, Christoph Scherber wrote:

> Hi!
> 
> OK, here are some more details on the function: My dataframe consists
> of several columns of categorical variables (let´s call them A,B,C)
> plus a column with a response variable y (which is arcsine-square root
> transformed proportions)
> 
> I am now trying to write a function that automatically gives me the
> back-transformed mean values + standard errors for y for each column
> in the dataframe. Ideally, this would be something like
> 

why not do it in several steps:

omit <- !is.na(yourdf$y)
transfy <- ((sin(yourdf$y[omit]))^2)*100
transm <- aggregatey(list(m=transfy), list(A,B,C,D), mean)
transs <- aggregate(list(s=transfy), list(A,B,C,D), function(x) 
(sd(x)/sqrt(length(x))) # I hope I have corect no of ()

cbind(transm,transs$s)

and if you feel like you can pack it to some function.

Cheers
Petr


> tapply(y,list(A,B,C,D),backtransformed.mean)
> 
> Here is the correct version of the function:
> 
> backsin<-function(x,y){
> backtransf<-list()
> 
> back<-((sin(x[x!="NA"]))^2)*100
> backtransf$mback<-tapply(back,y[x!="NA"],mean)
> backtransf$sdback<-tapply(back,y[x!="NA"],std)/sqrt(length(y[x!="NA"])
> ) backtransf }
> 
> 
> Regards,
> Christoph
> 
> 
> Petr Pikal wrote:
> 
> >Hi
> >
> >I am not sure if anybody gave you a reply, but do you think you gave
> >enough detail about your data, what you expect, what you did, what
> >was the response and how it differ from expected output and best of
> >all ***working*** example?
> >
> >BTW, what is stdev?
> >
> >If you wanted to compute standard deviation sd is enough.
> >
> >Cheers
> >Petr
> >
> >On 27 Jan 2005 at 12:20, Christoph Scherber wrote:
> >
> >  
> >
> >>Dear all,
> >>
> >>I´ve got a simple self-written function to calculate the mean + s.e.
> >>from arcsine-transformed data:
> >>
> >>backsin<-function(x,y,...){
> >> backtransf<-list()
> >> backtransf$back<-((sin(x[x!="NA"]))^2)*100
> >> backtransf$mback<-tapply(backtransf$back,y[x!="NA"],mean)
> >> backtransf$sdback<-tapply(backtransf$back,y[x!="NA"],std)/sqrt(leng
> >> th(y[x!="NA"])) 
> >>
> 
> >>backtransf
> >>    
> >>
> >>}
> >>
> >>I would like to apply this function to whole datasets, such as
> >>
> >>tapply(variable,list(A,B,C,D),backsin)
> >>
> >>Of course, this doesn´t work with the way in which the backsin()
> >>function is specified.
> >>
> >>Does anyone have suggestions on how I could improve my function?
> >>
> >>Regards,
> >>Christoph
> >>
> >>______________________________________________
> >>R-help at stat.math.ethz.ch mailing list
> >>https://stat.ethz.ch/mailman/listinfo/r-help
> >>PLEASE do read the posting guide!
> >>http://www.R-project.org/posting-guide.html
> >>    
> >>
> >
> >Petr Pikal
> >petr.pikal at precheza.cz
> >
> >
> >
> >  
> >
> 
> ______________________________________________
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Petr Pikal
petr.pikal at precheza.cz