AW: [R] Applying "by" results

[Jan_Svatos@eurotel.cz]

Oops,
I am terribly sorry, I recognized my mistake, as I thought
that the factors are ordered in PPress,

1    1 (k times)
1    2 (k times)
1    3 (k times)
etc...

Of course, "solution" I supplied is then not correct.
Thank you for your notice and for a more general solution.

Jan

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/- Jan Svatos,              Sokolovska 855/225 -/
/- Data Analyst,            Prague 9           -/
/- Eurotel Praha            190 00             -/
/- jan_svatos at eurotel.cz    Czechia            -/
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                    "Dieter Menne"                                                                                        
                    <dieter.menne at menne-           <Jan_Svatos at eurotel.cz>                                                
                    biomed.de>                                                                                            
                    07/31/01 11:36 AM              AW: [R] Applying "by" results                                          
                                                                                                                          
                                                                                                                          
                                                                                                                          



Jan,

I tried again, and I am sorry to say that your result is not correct.
I would only work if the data are ordered from the beginning
in the same order as they are processed.

See below: Press1 is not correct (not easy to see).
Press 2 is correct.

set.seed(13)
PPress<-data.frame(Marker=as.factor(c(rep(1,12),rep(2,12))),
                   Chan=as.factor(rep(1:4,6)), Press=rnorm(24) )
attach(PPress)
PPress$Press1<-unlist(by (Press,list(Marker,Chan), function(x) x-min(x)))

minp<-unlist(tapply(Press,list(Chan,Marker),min,simplify=F))
imin<-tapply(Press,list(Chan,Marker))
PPress$Press2<-Press-minp[imin]



Dieter




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