[R] Help with R: functions

From: Pryseley Assam <assampryseley_at_yahoo.com>
Date: Tue 31 Jan 2006 - 00:14:14 EST

Hello R-users    

  I am new to R and trying to write some functions. I have problems writing functions that takes a data set as an arguement and uses variables in the data. I illustrate my problem with a small example below:    

   sample data   #------------------

  visual24<-rnorm(30,3,5)
  visual52<-rt(30,7)
  dats<- data.frame(cbind(visual24,visual52))   remove(visual24, visual52)    

  # first code

  #--------------
  st <-function(data,x,y){
  rcc<-coef(lm(y~x))

  plot(x,y)
  abline(rcc[1],rcc[2])
}

  st(data=dats,x=dats$visual24,y=dats$visual52)    

  This code works fine, but with such a code the data as an arguement to the funtion is not necessary.   However, i wish to write a function that reads the variables from the data directly.   I tried using the function below but it does not work.    

  # second code

  #------------------

  st <-function(data,x,y){
  rcc<-coef(lm(data$y~data$x))
  plot(data$x,data$y)
  abline(rcc[1],rcc[2])
}

  st(dats,visual24,visual52)    

  I wish to inquire if any one has an idea of what i need to adjust in the function so that it works.   I believe that the referencing $x or $y in the function is not doing the correct thing.    

  Better still, will it be a problem if i code the functions as in the first code above?   I mean given that they will be used to create a library    

  Best regards
  Pryseley                     


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