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change values of a vector selectively

Mathieu Basille 
What about something along that line? It implies converting into numeric
and then back to factor to take benefit of each class:

(bli <- factor(c(1, 0,0,0,0,0, 2,0,0,0,0,0, "A", 0,0,0,0,2, 0,0,0,1)))

blo <- ifelse(bli != 0, as.numeric(bli), 0)

bla <- factor(cumsum(blo))
levels(bla) <- bli[bli != 0]
bla

You can remove the 'blo' step and doing the whole stuff in one line
(factor(cumsum(ifelse(...)))), but I thought it was easier to understand
that way. I haven't tested on a large dataset if it's more efficient
than the 'for' approach, though.

Hope this helps,
Mathieu.


Le 2011-01-11 09:58, B.-Markus Schuller a ?crit :

  
    

      
      
    

  


  


  


  
  

    

  

    
      
    
    
Thread (6 messages)

  

  

    
            
        B.-Markus Schuller
        
        change values of a vector selectively
      
      Jan 11
    
    
      
            
        Christian Parker
        
        change values of a vector selectively
      
      Jan 11
    
    
      
            
        syrovat at sci.muni.cz
        
        change values of a vector selectively
      
      Jan 11
    
    
      
            
        Christian Parker
        
        change values of a vector selectively
      
      Jan 11
    
    
      
            
        Andrew Rominger
        
        change values of a vector selectively
      
      Jan 11
    
    
      
            
        Mathieu Basille
        
        change values of a vector selectively
      
      Jan 11