Passing arguments to a list in tapply

Question

I'm new to R and having trouble with passing arguments to a function for a few days now.

I have a function that uses tapply with a by statement in it, My dataset is in the form of list data frames,so the function is:

Means = function(data,by,month){
   data1 = list() 
   for (i in 1:length(month)){
        data1[[i]] = tapply(data[[i]]$var1,by,mean)
   }
   data1
}

by should be a list of variables(unquoted), but the problem is calling the function, the variables are unrecognized:

temp = Means(data,list(data$var2,data$var3))

this doesn't work, the problem is that data is a list and it's not a data frame, is there a way to overpass it or should I reshape my data? One way is to do the for loop in the function calling, but I'd rather avoid it because that won't save me much writing using the function.

Thank you.

Answer 1

This works:

Means = function(data,by){

  data1 = tapply(data$Sepal.Length,by,mean)
  #return value of the function:
  data1
}

Means(iris, list(iris$Petal.Length, iris$Petal.Width))