FLR

Looks like you cant fix parameters in FLGrowth

# class FLGrowth
setClass('FLGrowth', representation('FLModel',
mass='FLArray'))

# constructor
setGeneric('FLGrowth', function(model, ...)
standardGeneric('FLGrowth'))

setMethod('FLGrowth', signature(model='ANY'),
function(model, ...)
return(FLModel(model, ..., class='FLGrowth')))

setMethod('FLGrowth', signature(model='missing'),
function(...)
return(FLModel(formula(NULL), ..., class='FLGrowth')))

# example
data(ple4)

gro <- FLGrowth(mass~(Minf*(1-exp(-k*(age-t0))))^3, mass=FLCohort(stock.wt(ple4)))

gro <- fmle(gro, start=list(Minf=7, k=0.3, t0=0), fixed=list(Minf=7))