Writing functions in R

Question

I am getting familiar with R after a good amount of experience with SAS and I've quickly discovered that functions in R do NOT behave like macros in SAS, so I need a little guidance.

Here is my function that doesn't work:

dscore<-function(data,var){

  ave<-mean(data$var)
  sd<-sd(data$var)

  data$vardscore<-(data$var-ave)/sd


  return(data)
}

I am using the cars dataset

cars<-dscore(cars,speed)

Should give me back the cars dataframe with an additional column that is the Cohen D value for the speed variable for that observation.

I get all sorts of crazy errors, so I would appreciate any help.

edit:

dbind<-function(data,var){
  var<-substitute(var)
  var<-as.character(var)
  ave<-mean(data[,var])
  sd<-sd(data[,var])
  name<-paste0(var,"dscore")
  data$name=((data[,var]-ave)/sd)
  return(data)
}

I need help dynamically naming the new column based on the input. Right now I just get a new column named "name"

Answer 1

You cannot use the $ sign with a variable. Try instead:

data[,var]

where var must be a character, e.g. "speed"

dscore<-function(data,var){

  ave<-mean(data[,var])
  sd<-sd(data[,var])

  data[,paste0(var,"dscore")]<-(data[,var]-ave)/sd


  return(data)
}

cars<-dscore(cars,var="speed")

Answer 2

dscore<-function(data,var){
  ave<-mean(data[,var])
  sd<-sd(data[,var])
  data$vardscore<-(data[,var]-ave)/sd
  return(data)
}
cars<-dscore(cars, "speed")