R help - May 2011 - Group close numbers in a vector

Hi everyone,
i am trying to group close numbers in a vector.
For example i have a vector x = [1 2 4 7 9 10 15].
I want the code to pick 1 2 4 (max difference between successive numbers is
2) and assign them to variable a, then pick 7 9 10 and assign them to b and
15 to c. But since i do not know how many groups there will be the code
should create a,b,c etc as it goes along. So if x = [1 2 4 7 9 10 15 20] it
should create a,b,c and d this time and assign 20 to d (while the others
remain the same).

any help will be appreciated,
thanks,
salih

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> Hi everyone,
> i am trying to group close numbers in a vector.
> For example i have a vector x = [1 2 4 7 9 10 15].
> I want the code to pick 1 2 4 (max difference between successive numbers 
> is
> 2) and assign them to variable a, then pick 7 9 10 and assign them to b 
> and
> 15 to c. But since i do not know how many groups there will be the code
> should create a,b,c etc as it goes along. So if x = [1 2 4 7 9 10 15 20] 
> it
> should create a,b,c and d this time and assign 20 to d (while the others
> remain the same).
I think the following function should do basically what you want:
codeit = function(x){
  action = c(TRUE, diff(x) <= 2)
  g = paste('x', '1', sep='')
  j = 1
  for (i in 2: length(x)){
    if (action[i-1] != action[i] | action[i] == FALSE) j = j+1
      g[i] = paste('x', j, sep='')
  }
  df = data.frame(x, grp.x=g)
}




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Robert W. Baer, Ph.D.
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