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# Part of the rstanarm package for estimating model parameters
# Copyright (C) 2016 Trustees of Columbia University
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 3
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#' Bayesian nonlinear models with group-specific terms via Stan
#'
#' \if{html}{\figure{stanlogo.png}{options: width="25px" alt="http://mc-stan.org/about/logo/"}}
#' Bayesian inference for NLMMs with group-specific coefficients that have
#' unknown covariance matrices with flexible priors.
#'
#' @export
#' @templateVar fun stan_nlmer
#' @templateVar pkg lme4
#' @templateVar pkgfun nlmer
#' @template return-stanreg-object
#' @template see-also
#' @template args-dots
#' @template args-prior_aux
#' @template args-priors
#' @template args-prior_PD
#' @template args-algorithm
#' @template args-adapt_delta
#' @template args-sparse
#' @template args-QR
#'
#' @param formula,data Same as for \code{\link[lme4]{nlmer}}. \emph{We strongly
#' advise against omitting the \code{data} argument}. Unless \code{data} is
#' specified (and is a data frame) many post-estimation functions (including
#' \code{update}, \code{loo}, \code{kfold}) are not guaranteed to work
#' properly.
#' @param subset,weights,offset Same as \code{\link[stats]{glm}}.
#' @param na.action,contrasts Same as \code{\link[stats]{glm}}, but rarely
#' specified.
#' @param prior_covariance Cannot be \code{NULL}; see \code{\link{decov}} for
#' more information about the default arguments.
#'
#' @details The \code{stan_nlmer} function is similar in syntax to
#' \code{\link[lme4]{nlmer}} but rather than performing (approximate) maximum
#' marginal likelihood estimation, Bayesian estimation is by default performed
#' via MCMC. The Bayesian model adds independent priors on the "coefficients"
#' --- which are really intercepts --- in the same way as
#' \code{\link{stan_nlmer}} and priors on the terms of a decomposition of the
#' covariance matrices of the group-specific parameters. See
#' \code{\link{priors}} for more information about the priors.
#'
#' The supported transformation functions are limited to the named
#' "self-starting" functions in the \pkg{stats} library:
#' \code{\link[stats]{SSasymp}}, \code{\link[stats]{SSasympOff}},
#' \code{\link[stats]{SSasympOrig}}, \code{\link[stats]{SSbiexp}},
#' \code{\link[stats]{SSfol}}, \code{\link[stats]{SSfpl}},
#' \code{\link[stats]{SSgompertz}}, \code{\link[stats]{SSlogis}},
#' \code{\link[stats]{SSmicmen}}, and \code{\link[stats]{SSweibull}}.
#'
#'
#' @seealso The vignette for \code{stan_glmer}, which also discusses
#' \code{stan_nlmer} models. \url{http://mc-stan.org/rstanarm/articles/}
#'
#' @examples
#' \donttest{
#' data("Orange", package = "datasets")
#' Orange$circumference <- Orange$circumference / 100
#' Orange$age <- Orange$age / 100
#' fit <- stan_nlmer(
#' circumference ~ SSlogis(age, Asym, xmid, scal) ~ Asym|Tree,
#' data = Orange,
#' # for speed only
#' chains = 1,
#' iter = 1000
#' )
#' print(fit)
#' posterior_interval(fit)
#' plot(fit, regex_pars = "b\\[")
#' }
#' @importFrom lme4 nlformula
#' @importFrom stats getInitial
stan_nlmer <-
function(formula,
data = NULL,
subset,
weights,
na.action,
offset,
contrasts = NULL,
...,
prior = normal(autoscale=TRUE),
prior_aux = exponential(autoscale=TRUE),
prior_covariance = decov(),
prior_PD = FALSE,
algorithm = c("sampling", "meanfield", "fullrank"),
adapt_delta = NULL,
QR = FALSE,
sparse = FALSE) {
if (!has_outcome_variable(formula[[2]])) {
stop("LHS of formula must be specified.")
}
f <- as.character(formula[-3])
SSfunctions <- grep("^SS[[:lower:]]+", ls("package:stats"), value = TRUE)
SSfun <- sapply(SSfunctions, function(ss)
grepl(paste0(ss, "("), x = f[2], fixed = TRUE))
if (!any(SSfun)) {
stop("'stan_nlmer' requires a named self-starting nonlinear function.")
}
SSfun <- which(SSfun)
SSfun_char <- names(SSfun)
mc <- match.call(expand.dots = FALSE)
mc$prior <- mc$prior_aux <- mc$prior_covariance <- mc$prior_PD <-
mc$algorithm <- mc$adapt_delta <- mc$QR <- mc$sparse <- NULL
mc$start <-
unlist(getInitial(
object = as.formula(f[-1]),
data = data,
control = list(maxiter = 0, warnOnly = TRUE)
))
nlf <- nlformula(mc)
X <- nlf$X
y <- nlf$respMod$y
weights <- nlf$respMod$weights
offset <- nlf$respMod$offset
nlf$reTrms$SSfun <- SSfun
nlf$reTrms$decov <- prior_covariance
nlf_inputs <- parse_nlf_inputs(nlf$respMod)
if (SSfun_char == "SSfol") {
nlf$reTrms$Dose <- nlf$frame[[nlf_inputs[2]]]
nlf$reTrms$input <- nlf$frame[[nlf_inputs[3]]]
} else {
nlf$reTrms$input <- nlf$frame[[nlf_inputs[2]]]
}
algorithm <- match.arg(algorithm)
stanfit <- stan_glm.fit(x = X, y = y, family = gaussian(link = "identity"),
weights = weights, offset = offset,
prior = prior, prior_intercept = NULL,
prior_aux = prior_aux, prior_PD = prior_PD,
algorithm = algorithm, adapt_delta = adapt_delta,
group = nlf$reTrms, QR = QR, sparse = sparse, ...)
if (algorithm != "optimizing" && !is(stanfit, "stanfit")) {
return(stanfit)
}
if (SSfun_char == "SSfpl") { # SSfun = 6
stanfit@sim$samples <- lapply(stanfit@sim$samples, FUN = function(x) {
x[[4L]] <- exp(x[[4L]])
return(x)
})
} else if (SSfun_char == "SSlogis") { # SSfun = 8
stanfit@sim$samples <- lapply(stanfit@sim$samples, FUN = function(x) {
x[[3L]] <- exp(x[[3L]])
return(x)
})
}
Z <- pad_reTrms(Ztlist = nlf$reTrms$Ztlist, cnms = nlf$reTrms$cnms,
flist = nlf$reTrms$flist)$Z
colnames(Z) <- b_names(names(stanfit), value = TRUE)
fit <- nlist(stanfit,
family = make_nlf_family(SSfun_char, nlf),
formula, offset, weights,
x = cbind(X, Z), y = y, data, call = match.call(), terms = NULL,
model = NULL, na.action = na.omit, contrasts, algorithm,
glmod = nlf, stan_function = "stan_nlmer")
out <- stanreg(fit)
class(out) <- c(class(out), "nlmerMod", "lmerMod")
return(out)
}
# internal ----------------------------------------------------------------
# @param respMod The respMod slot of the object returned by nlformula
# @return A character vector, the first element of which is the name of the SS
# function and the rest of the elements are the names of the arguments to the
# SS function
parse_nlf_inputs <- function(respMod) {
inputs <- as.character(respMod$nlmod[2])
inputs <- sub("(", ",", inputs, fixed = TRUE)
inputs <- sub(")", "", inputs, fixed = TRUE)
scan(
text = inputs,
what = character(),
sep = ",",
strip.white = TRUE,
quiet = TRUE
)
}
# Make family object
#
# @param SSfun_char SS function name as a string
# @param nlf Object returned by nlformula
# @return A family object
make_nlf_family <- function(SSfun_char, nlf) {
g <- gaussian(link = "identity")
g$link <- paste("inv", SSfun_char, sep = "_")
g$linkinv <- function(eta, arg1, arg2 = NULL, FUN = SSfun_char) {
if (is.matrix(eta)) {
len <- length(arg1)
nargs <- ncol(eta) / len
SSargs <- lapply(1:nargs, FUN = function(i) {
start <- 1 + (i - 1) * len
end <- i * len
t(eta[, start:end, drop = FALSE])
})
if (is.null(arg2)) SSargs <- c(list(arg1), SSargs)
else SSargs <- c(list(arg1, arg2), SSargs)
} else {
SSargs <- as.data.frame(matrix(eta, nrow = length(arg1)))
if (is.null(arg2)) SSargs <- cbind(arg1, SSargs)
else SSargs <- cbind(arg1, arg2, SSargs)
}
names(SSargs) <- names(formals(FUN))
if (FUN == "SSbiexp")
SSargs$A1 <- SSargs$A1 + exp(SSargs$A2)
do.call(FUN, args = SSargs)
}
nlf_inputs <- parse_nlf_inputs(nlf$respMod)
if (SSfun_char == "SSfol") {
formals(g$linkinv)$arg1 <- nlf$frame[[nlf_inputs[2]]]
formals(g$linkinv)$arg2 <- nlf$frame[[nlf_inputs[3]]]
} else {
formals(g$linkinv)$arg1 <- nlf$frame[[nlf_inputs[2]]]
}
g$linkfun <- function(mu) stop("'linkfun' should not have been called")
g$variance <- function(mu) stop("'variance' should not have been called")
g$mu.eta <- function(mu) stop("'mu.eta' should not have been called")
return(g)
}
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