I_optim: Interface of unified optimization functions.

In phenofit: Extract Remote Sensing Vegetation Phenology

Interface of unified optimization functions.

Description

optimx speed is not satisfied. So I_optim is present.

• I_optim: Interface of unified optimization functions.

• I_optimx: deprecated, which is about 10 times slower than I_optim.

Usage

I_optim(prior, FUN, y, t, method = "BFGS", ..., use.cpp = FALSE)

I_optimx(prior, FUN, y, t, method, verbose = FALSE, ..., use.cpp = FALSE)

Arguments

prior	A vector of initial values for the parameters for which optimal values are to be found. prior is suggested giving a column name.
FUN	Fine curve fitting function for goal function f_goal().
y	Numeric vector, vegetation index time-series
t	Numeric vector, Date variable
method	method can be some of ⁠'BFGS','CG','Nelder-Mead', 'L-BFGS-B', 'nlm', 'nlminb', 'ucminf'⁠. For I_optimx, other methods are also supported, e.g. ⁠'spg','Rcgmin','Rvmmin', 'newuoa','bobyqa','nmkb','hjkb'⁠.
...	other parameters passed to I_optim() or I_optimx().
use.cpp	(unstable, not used) boolean, whether to use c++ defined fine fitting function? If FALSE, R version will be used.
verbose	If TRUE, all optimization methods in optimx::optimx() are used, and print optimization information of all methods.

Value

• convcode: An integer code. 0 indicates successful convergence. Various methods may or may not return sufficient information to allow all the codes to be specified. An incomplete list of codes includes

  • 1: indicates that the iteration limit maxit had been reached.

  • 20: indicates that the initial set of parameters is inadmissible, that is, that the function cannot be computed or returns an infinite, NULL, or NA value.

  • 21: indicates that an intermediate set of parameters is inadmissible.

  • 10: indicates degeneracy of the Nelder–Mead simplex.

  • 51: indicates a warning from the "L-BFGS-B" method; see component message for further details.

  • 52: indicates an error from the "L-BFGS-B" method; see component message for further details.

  • 9999: error

• value: The value of fn corresponding to par

• par: The best parameter found

• nitns: the number of iterations

• fevals: The number of calls to objective.

See Also

stats::optim(), stats::nlminb(), stats::nlm(), optimx::optimx(), ucminf::ucminf()

Examples

# simulate vegetation time-series
FUN  = doubleLog_Beck
par  = c( mn  = 0.1 , mx  = 0.7 , sos = 50 , rsp = 0.1 , eos = 250, rau = 0.1)
par0 = c( mn  = 0.15, mx  = 0.65, sos = 100, rsp = 0.12, eos = 200, rau = 0.12)

t <- seq(1, 365, 8)
y <- FUN(par, t)

methods = c("BFGS", "ucminf", "nlm", "nlminb")
opt1 <- I_optim (par0, FUN, y, t, methods)
opt2 <- I_optimx(par0, FUN, y, t, methods)

# \dontrun{
# microbenchmark::microbenchmark(
#     opt1 = I_optim (par0, FUN, y, t, methods),
#     opt2 = I_optimx(par0, FUN, y, t, methods),
#     times = 2
# )
# }

phenofit documentation built on May 29, 2024, 2:39 a.m.