Question

I’m trying to use the following code in R:

ID=seq(1,11)
g=c(1,2,3,1,1,2,3,4,4,1,3)
x <- sample(11)
d <- data.frame(ID,g, x)

Ranking_Categoria<-function(d,var,category)
{
  d$rank<-ave(d$var,d$category,FUN=rank)
  return(d)
}

and I get the following error message:

Error in split.default(x, g) : first argument must be a vector. 

Variables var and category (character) are columns of the dataframe d that user needs to specify in order to get the desired result. I need to refer to this names when I use the function ave() as you can see.

Answer 1

You need to use [[ to get the var and category columns by name:

Ranking_Categoria<-function(d,var,category)
{
  d$rank<-ave(d[[var]],d[[category]],FUN=rank)
  return(d)
}

… because d$var tries to get the column called “var”, and there is none.

UPDATE

> Ranking_Categoria(d, "x", "g")
   ID g  x rank
1   1 1 10    3
2   2 2  9    2
3   3 3  4    1
4   4 1 11    4
5   5 1  1    1
6   6 2  8    1
7   7 3  6    2
8   8 4  2    1
9   9 4  5    2
10 10 1  3    2
11 11 3  7    3