% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/train.R
\name{train}
\alias{train}
\title{Train Random Forests}
\usage{
train(formula, data, splitFinder = NULL, nodeResponseCombiner = NULL,
  forestResponseCombiner = NULL, ntree, numberOfSplits, mtry, nodeSize,
  maxNodeDepth = 1e+05, na.penalty = TRUE, splitPureNodes = TRUE,
  savePath = NULL, savePath.overwrite = c("warn", "delete", "merge"),
  cores = getCores(), randomSeed = NULL, displayProgress = TRUE)
}
\arguments{
\item{formula}{You may specify the response and covariates as a formula
instead; make sure the response in the formula is still properly
constructed.}

\item{data}{A data.frame containing the columns of the predictors and
responses.}

\item{splitFinder}{A split finder that's used to score splits in the random
forest training algorithm. See \code{\link{CompetingRiskSplitFinders}} or
\code{\link{WeightedVarianceSplitFinder}}. If you don't specify one, this
function tries to pick one based on the response. For
\code{\link{CR_Response}} without censor times, it will pick a
\code{\link{LogRankSplitFinder}}; while if censor times were provided it
will pick \code{\link{GrayLogRankSplitFinder}}; for integer or numeric
responses it picks a \code{\link{WeightedVarianceSplitFinder}}.}

\item{nodeResponseCombiner}{A response combiner that's used to combine
responses for each terminal node in a tree (regression example; average the
observations in each tree into a single number). See
\code{\link{CR_ResponseCombiner}} or \code{\link{MeanResponseCombiner}}. If
you don't specify one, this function tries to pick one based on the
response. For \code{\link{CR_Response}} it picks a
\code{\link{CR_ResponseCombiner}}; for integer or numeric responses it
picks a \code{\link{MeanResponseCombiner}}.}

\item{forestResponseCombiner}{A response combiner that's used to combine
predictions across trees into one final result (regression example; average
the prediction of each tree into a single number). See
\code{\link{CR_FunctionCombiner}} or \code{\link{MeanResponseCombiner}}. If
you don't specify one, this function tries to pick one based on the
response. For \code{\link{CR_Response}} it picks a
\code{\link{CR_FunctionCombiner}}; for integer or numeric responses it
picks a \code{\link{MeanResponseCombiner}}.}

\item{ntree}{An integer that specifies how many trees should be trained.}

\item{numberOfSplits}{A tuning parameter specifying how many random splits
should be tried for a covariate; a value of 0 means all splits will be
tried (with an exception for factors, who might have too many splits to
feasibly compute).}

\item{mtry}{A tuning parameter specifying how many covariates will be
randomly chosen to be tried in the splitting process. This value must be at
least 1.}

\item{nodeSize}{The algorithm will not attempt to split a node that has
observations less than 2*\code{nodeSize}; this guarantees that any two
sibling terminal nodes together have an average size of at least
\code{nodeSize}; note that it doesn't guarantee that every node is at least
as large as \code{nodeSize}.}

\item{maxNodeDepth}{This parameter is analogous to \code{nodeSize} in that it
controls tree length; by default \code{maxNodeDepth} is an extremely high
number and tree depth is controlled by \code{nodeSize}.}

\item{na.penalty}{This parameter controls whether predictor variables with
NAs should be penalized when being considered for a best split. Best splits
(and the associated score) are determined on only non-NA data; the penalty
is to take the best split identified, and to randomly assign any NAs
(according to the proportion of data split left and right), and then
recalculate the corresponding split score, when is then compared with the
other split candiate variables. This penalty adds some computational time,
so it may be disabled for some variables. \code{na.penalty} may be
specified as a vector of logicals indicating, for each predictor variable,
whether the penalty should be applied to that variable. If it's length 1
then it applies to all variables. Alternatively, a single numeric value may
be provided to indicate a threshold whereby the penalty is activated only
if the proportion of NAs for that variable in the training set exceeds that
threshold.}

\item{splitPureNodes}{This parameter determines whether the algorithm will
split a pure node. If set to FALSE, then before every split it will check
that every response is the same, and if so, not split. If set to TRUE it
forgoes that check and splits it. Prediction accuracy won't change under
any sensible \code{nodeResponseCombiner}; as all terminal nodes from a
split pure node should give the same prediction, so this parameter only
affects performance. If your response is continuous you'll likely
experience faster train times by setting it to TRUE. Default value is TRUE.}

\item{savePath}{If set, this parameter will save each tree of the random
forest in this directory as the forest is trained. Use this parameter if
you need to save memory while training. See also \code{\link{loadForest}}}

\item{savePath.overwrite}{This parameter controls the behaviour for what
happens if \code{savePath} is pointing to an existing directory. If set to
\code{warn} (default) then \code{train} refuses to proceed. If set to
\code{delete} then all the contents in that folder are deleted for the new
forest to be trained. Note that all contents are deleted, even those files
not related to \code{largeRCRF}. Use only if you're sure it's safe. If set
to \code{merge}, then the files describing the forest (such as its
parameters) are overwritten but the saved trees are not. The algorithm
assumes (without checking) that the existing trees are from a previous run
and starts from where it left off. This option is useful if recovering from
a crash.}

\item{cores}{This parameter specifies how many trees will be simultaneously
trained. By default the package attempts to detect how many cores you have
by using the \code{parallel} package and using all of them. You may specify
a lower number if you wish. It is not recommended to specify a number
greater than the number of available cores as this will hurt performance
with no available benefit.}

\item{randomSeed}{This parameter specifies a random seed if reproducible,
deterministic forests are desired.}

\item{displayProgress}{A logical indicating whether the progress should be
displayed to console; default is \code{TRUE}. Useful to set to FALSE in
some automated situations.}
}
\value{
A \code{JRandomForest} object. You may call \code{predict} or
  \code{print} on it.
}
\description{
Trains the random forest. The type of response the random forest can be
trained on varies depending on the \code{splitFinder},
\code{nodeResponseCombiner}, and the \code{forestResponseCombiner}
parameters. Make sure these are compatible with each other, and with the
response you plug in. \code{splitFinder} should work on the responses you are
providing; \code{nodeResponseCombiner} should combine these responses into
some intermediate product, and \code{forestResponseCombiner} combines these
intermediate products into the final output product. Note that
\code{nodeResponseCombiner} and \code{forestResponseCombiner} can be inferred
from the data (so feel free to not specify them), and \code{splitFinder} can
be inferred but you might want to change its default.
}
\note{
If saving memory is a concern, you can replace \code{covariateData} or
  \code{data} with an environment containing one element called \code{data}
  as the actual dataset. After the data has been imported into Java, but
  before the forest training begins, the dataset in the environment is
  deleted, freeing up memory in R.
}
\examples{
# Regression Example
x1 <- rnorm(1000)
x2 <- rnorm(1000)
y <- 1 + x1 + x2 + rnorm(1000)

data <- data.frame(x1, x2, y)
forest <- train(y ~ x1 + x2, data, WeightedVarianceSplitFinder(),
  MeanResponseCombiner(), MeanResponseCombiner(), ntree=100,
  numberOfSplits = 5, mtry = 1, nodeSize = 5)

# Fix x2 to be 0
newData <- data.frame(x1 = seq(from=-2, to=2, by=0.5), x2 = 0)
ypred <- predict(forest, newData)

plot(ypred ~ newData$x1, type="l")

# Competing Risk Example
x1 <- abs(rnorm(1000))
x2 <- abs(rnorm(1000))

T1 <- rexp(1000, rate=x1)
T2 <- rweibull(1000, shape=x1, scale=x2)
C <- rexp(1000)
u <- pmin(T1, T2, C)
delta <- ifelse(u==T1, 1, ifelse(u==T2, 2, 0))

data <- data.frame(x1, x2)

forest <- train(CR_Response(delta, u) ~ x1 + x2, data,
   LogRankSplitFinder(1:2), CR_ResponseCombiner(1:2),
   CR_FunctionCombiner(1:2), ntree=100, numberOfSplits=5,
   mtry=1, nodeSize=10)
newData <- data.frame(x1 = c(-1, 0, 1), x2 = 0)
ypred <- predict(forest, newData)
}
\seealso{
\code{\link{predict.JRandomForest}}
}