How to calculate relative fitness from absolute fitness with recapture data?
So the dataset is this: 

  id   x3 x4
   2    1  1  
   3    1  1  
   4    1  1  
   5    1  0  


Lets assume that we caught the entire population so that we know that a 0 is really a dead organism (the estimate is proportional to lifetime fitness). Furthermore, there is no density-dependent selection and the generations are non overlapping. 

The survival for next year would be the fitness value of all individual. So in year x4, the absolute fitness would be W = c(1,1,1,0). Then the mean absolute  fitness would be: W_bar = (1+1+1+0)/4 = 3/4. Then to get w, the relative fitness, you divide W by W_bar. w = c(4/3, 4/3, 4/3, 0). Therefor, if you calculate mean(W/W_bar), it should give you 1.

This is as in Endler, J. A. 1986. Natural Selection in the Wild. Princeton University Press, p. 168.