[R] vectorisation suggestion

[Federico Calboli]

Hi All,

I am counting the number of occurrences of the terms listed in one  
vector in another vector.

My code runs:

for( i in 1:length(vector3)){
   vector3[i]  = sum(1*is.element(vector2,  vector1[i]))
}

where

vector1 = vector containing the terms whose occurrences I want to count
vector2 = made up of a number of repetitions of all the elements of  
vector1
vector3 = a vector of NAs that is meant to get the result of the  
counting

My problem is that vector1 is about 60000 terms, and vector2 is  
620000... can anyone suggest a faster code than the one I wrote?

Cheers,

Federico Calboli


--
Federico C. F. Calboli
Department of Epidemiology and Public Health
Imperial College, St. Mary's Campus
Norfolk Place, London W2 1PG

Tel +44 (0)20 75941602   Fax +44 (0)20 75943193

f.calboli [.a.t] imperial.ac.uk
f.calboli [.a.t] gmail.com