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# File .../lmrobPredict.R
# Part of the R package 'robustbase', http://www.R-project.org
# Based on predict.lm (cf. src/library/stats/R/lm.R)
#
# 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 2 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.
#
# A copy of the GNU General Public License is available at
# http://www.r-project.org/Licenses/
# Note that '# *rob' indicate adjustment for the robust case
predict.lmrob <-
function(object, newdata, se.fit = FALSE, scale = NULL, df = NULL, # *rob
interval = c("none", "confidence", "prediction"),
level = .95, type = c("response", "terms"),
terms = NULL, na.action = na.pass, pred.var = res.var/weights,
weights = 1, ...)
{
tt <- terms(object)
if(!inherits(object, "lmrob") && !inherits(object, "glmrob")) # *rob
warning("calling predict.lm(<fake-lmrob-object>) ...") # *rob
if(missing(newdata) || is.null(newdata)) {
mm <- X <- model.matrix.lm(object)
mmDone <- TRUE
offset <- object$offset
}
else {
Terms <- delete.response(tt)
m <- model.frame(Terms, newdata, na.action = na.action,
xlev = object$xlevels)
if(!is.null(cl <- attr(Terms, "dataClasses"))) .checkMFClasses(cl, m)
X <- model.matrix(Terms, m, contrasts.arg = object$contrasts)
offset <- rep.int(0, nrow(X))
if (!is.null(off.num <- attr(tt, "offset")))
for(i in off.num)
offset <- offset + eval(attr(tt, "variables")[[i+1]], newdata)
if (!is.null(object$call$offset))
offset <- offset + eval(object$call$offset, newdata)
mmDone <- FALSE
}
n <- length(object$residuals) # NROW(qr(object)$qr)
p <- object$rank
if(is.null(p)) { # *rob
df <- Inf
p <- sum(!is.na(coef(object)))
piv <- seq_len(p)
} else {
p1 <- seq_len(p)
piv <- if(p) qr(object)$pivot[p1]
}
if(p < ncol(X) && !(missing(newdata) || is.null(newdata)))
warning("prediction from a rank-deficient fit may be misleading")
beta <- object$coefficients
X.piv <- X[, piv, drop = FALSE]
predictor <- drop(X.piv %*% beta[piv])
if (!is.null(offset))
predictor <- predictor + offset
interval <- match.arg(interval)
if (interval == "prediction") {
if (missing(newdata)) { # *rob: this and next if statement are combined
warning("Predictions on current data refer to _future_ responses")
if (missing(weights)) {
w <- weights(object) # *rob
if (!is.null(w)) {
weights <- w
warning("Assuming prediction variance inversely proportional to weights used for fitting")
}
}
}
if (!missing(newdata) && missing(weights) && !is.null(object$weights) && missing(pred.var))
warning("Assuming constant prediction variance even though model fit is weighted")
if (inherits(weights, "formula")){
if (length(weights) != 2L)
stop("'weights' as formula should be one-sided")
d <- if(missing(newdata) || is.null(newdata))
model.frame(object)
else
newdata
weights <- eval(weights[[2L]], d, environment(weights))
}
}## "prediction" interval
type <- match.arg(type)
if(se.fit || interval != "none") {# *rob: whole 'then' statement is different
df <- object$df.residual
res.var <- if (is.null(scale)) object$s^2 else scale^2
ip <- if(type != "terms")
diag(X.piv %*% object$cov %*% t(X.piv)) else rep.int(0, n)
}
if (type == "terms") { ## type == "terms" ------------
if(!mmDone){
mm <- model.matrix.lm(object) # *rob: call of model.matrix.lm
# instead of model.matrix
mmDone <- TRUE
}
aa <- attr(mm, "assign")
ll <- attr(tt, "term.labels")
hasintercept <- attr(tt, "intercept") > 0L
if (hasintercept) ll <- c("(Intercept)", ll)
aaa <- factor(aa, labels = ll)
asgn <- split(order(aa), aaa)
if (hasintercept) {
asgn$"(Intercept)" <- NULL
if(!mmDone){
mm <- model.matrix.lm(object) # *rob: call of model.matrix.lm
# instead of model.matrix
mmDone <- TRUE
}
avx <- colMeans(mm)
termsconst <- sum(avx[piv] * beta[piv])
}
nterms <- length(asgn)
if(nterms > 0) {
predictor <- matrix(ncol = nterms, nrow = NROW(X))
dimnames(predictor) <- list(rownames(X), names(asgn))
if (se.fit || interval != "none") {
ip <- predictor # *rob: just this assignment is needed
}
if(hasintercept)
X <- sweep(X, 2L, avx, check.margin=FALSE)
unpiv <- rep.int(0L, NCOL(X))
unpiv[piv] <- p1
for (i in seq.int(1L, nterms, length.out = nterms)) {
iipiv <- asgn[[i]] # Columns of X, ith term
ii <- unpiv[iipiv] # Corresponding rows of cov
iipiv[ii == 0L] <- 0L
predictor[, i] <-
if(any(iipiv > 0L)) X[, iipiv, drop = FALSE] %*% beta[iipiv]
else 0
if (se.fit || interval != "none"){
ip[, i] <- if(any(iipiv > 0L)){# *rob: next steps modified
h.X <- X[, iipiv, drop = FALSE]
diag(h.X %*% object$cov[ii, ii] %*% t(h.X))
} else 0
}
}
if (!is.null(terms)) {
predictor <- predictor[, terms, drop = FALSE]
if (se.fit)
ip <- ip[, terms, drop = FALSE]
}
} else { # no terms
predictor <- ip <- matrix(0, n, 0L)
}
attr(predictor, 'constant') <- if (hasintercept) termsconst else 0
}
### Now construct elements of the list that will be returned
if(interval != "none") {
tfrac <- qt((1 - level)/2, df)
hwid <- tfrac * switch(interval,
confidence = sqrt(ip),
prediction = sqrt(ip+pred.var)
)
if(type != "terms") {
predictor <- cbind(predictor, predictor + hwid %o% c(1, -1))
colnames(predictor) <- c("fit", "lwr", "upr")
} else {
if (!is.null(terms)) hwid <- hwid[, terms, drop = FALSE]
lwr <- predictor + hwid
upr <- predictor - hwid
}
}
if(se.fit || interval != "none") {
se <- sqrt(ip)
if (type == "terms" && !is.null(terms)) se <- se[, terms, drop = FALSE]
}
if(missing(newdata) && !is.null(na.act <- object$na.action)) {
predictor <- napredict(na.act, predictor)
if(se.fit) se <- napredict(na.act, se)
}
if(type == "terms" && interval != "none") {
if(missing(newdata) && !is.null(na.act)) {
lwr <- napredict(na.act, lwr)
upr <- napredict(na.act, upr)
}
list(fit = predictor, se.fit = se, lwr = lwr, upr = upr,
df = df, residual.scale = sqrt(res.var))
} else if (se.fit)
list(fit = predictor, se.fit = se,
df = df, residual.scale = sqrt(res.var))
else predictor
}
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