[R] self-written function

[Christoph Scherber]

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

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(length(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
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>>PLEASE do read the posting guide!
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>>    
>>
>
>Petr Pikal
>petr.pikal at precheza.cz
>
>
>
>  
>