[R] Technological/Logistic substitution model.

[Peter Maclean]

 Any one with an idea of estimating the Technological/Logistic substitution model. 
The model is specified as: 
fi(t(j)) = 1/[1-exp(-alpa(t(i))-beta(i)] for t 0 
fi(t(j)) = 1-sum(f(j-1))- sum(f(j+1)) for tb <=t <= tc 
fi(t(j)) = 1/[1+ exp(alpas(t(i)-betas(i))] for t >=tc and alphas >0. T
The model assume that n technologies are introduced to the market, where 1 is the oldest and technology n is the newest, i and j are subscripts representing the type of technology, fi is the market share, t is a subscript denoting time, alpha, alphas, beta, and betas are parameters, tb and tc are time periods during which the technology i starts to enter the saturation and decline phase, respectively. Any suggestion, reading will be appreciate. 
 
Peter Maclean
Department of Economics
UDSM