diff --git a/NAMESPACE b/NAMESPACE
index c60de41..402bb00 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -35,4 +35,5 @@ export(loadForest)
 export(naiveConcordance)
 export(saveForest)
 export(train)
+export(vimp)
 import(rJava)
diff --git a/R/cr_integratedBrierScore.R b/R/cr_integratedBrierScore.R
index 9525238..a86645e 100644
--- a/R/cr_integratedBrierScore.R
+++ b/R/cr_integratedBrierScore.R
@@ -59,45 +59,14 @@ integratedBrierScore <- function(responses, predictions, event, time, censoringD
   
   java.censoringDistribution <- NULL
   if(!is.null(censoringDistribution)){
-    if(is.numeric(censoringDistribution)){
-      # estimate ECDF
-      censoringTimes <- .jarray(censoringDistribution, "D")
-      java.censoringDistribution <- .jcall(.class_Utils, makeResponse(.class_RightContinuousStepFunction), "estimateOneMinusECDF", censoringTimes)
-      
-    } else if(is.list(censoringDistribution)){
-      # First check that censoringDistribution fits the correct format
-      if(is.null(censoringDistribution$x) | is.null(censoringDistribution$y)){
-        stop("If the censoringDistribution is provided as a list, it must have an x and a y item that are numeric.")
-      }
-      
-      if(length(censoringDistribution$x) != length(censoringDistribution$y)){
-        stop("x and y in censoringDistribution must have the same length.")
-      }
-      
-      if(!is.numeric(censoringDistribution$x) | !is.numeric(censoringDistribution$y)){
-        stop("x and y in censoringDistribution must both be numeric.")
-      }
-      
-      java.censoringDistribution <- createRightContinuousStepFunction(censoringDistribution$x, censoringDistribution$y, defaultY = 1.0)
-      
-    } else if("stepfun" %in% class(censoringDistribution)){
-      x <- stats::knots(censoringDistribution)
-      y <- censoringDistribution(x)
-      
-      java.censoringDistribution <- createRightContinuousStepFunction(x, y, defaultY = 1.0)
-    }
-    else{
-      stop("Invalid censoringDistribution")
-    }
-    
-    # Make sure we wrap it in an Optional
+    java.censoringDistribution <- processCensoringDistribution(censoringDistribution)
     java.censoringDistribution <- .object_Optional(java.censoringDistribution)
-    
   }
   else{
     java.censoringDistribution <- .object_Optional(NULL)
   }
   
+  
   predictions.java <- lapply(predictions, function(x){return(x$javaObject)})
   predictions.java <- convertRListToJava(predictions.java)
   
diff --git a/R/java_classes_directory.R b/R/java_classes_directory.R
index 97598c3..8ffe241 100644
--- a/R/java_classes_directory.R
+++ b/R/java_classes_directory.R
@@ -10,6 +10,7 @@
 .class_Collection <- "java/util/Collection"
 .class_Serializable <- "java/io/Serializable"
 .class_File <- "java/io/File"
+.class_Random <- "java/util/Random"
 
 # Utility Classes
 .class_DataUtils <- "ca/joeltherrien/randomforest/utils/DataUtils"
@@ -53,6 +54,14 @@
 .class_LogRankSplitFinder <- "ca/joeltherrien/randomforest/responses/competingrisk/splitfinder/LogRankSplitFinder"
 .class_WeightedVarianceSplitFinder <- "ca/joeltherrien/randomforest/responses/regression/WeightedVarianceSplitFinder"
 
+# VIMP classes
+.class_IBSCalculator <- "ca/joeltherrien/randomforest/responses/competingrisk/IBSCalculator"
+.class_ErrorCalculator <- "ca/joeltherrien/randomforest/tree/vimp/ErrorCalculator"
+.class_RegressionErrorCalculator <- "ca/joeltherrien/randomforest/tree/vimp/RegressionErrorCalculator"
+.class_IBSErrorCalculatorWrapper <- "ca/joeltherrien/randomforest/tree/vimp/IBSErrorCalculatorWrapper"
+.class_VariableImportanceCalculator <- "ca/joeltherrien/randomforest/tree/vimp/VariableImportanceCalculator"
+
+
 .object_Optional <- function(object=NULL){
   if(is.null(object)){
     return(.jcall("java/util/Optional", "Ljava/util/Optional;", "empty"))
diff --git a/R/loadData.R b/R/loadData.R
index 9e870c2..7a1c0df 100644
--- a/R/loadData.R
+++ b/R/loadData.R
@@ -18,7 +18,7 @@ loadData <- function(data, xVarNames, responses, covariateList.java = NULL){
   rowList <- .jcall(.class_RUtils, makeResponse(.class_List), "importDataWithResponses",
                     responses$javaObject, covariateList.java, textData)
 
-  return(list(covariateList=covariateList.java, dataset=rowList))
+  return(list(covariateList = covariateList.java, dataset = rowList, responses = responses))
 
 }
 
@@ -54,15 +54,7 @@ getCovariateList <- function(data, xvarNames){
 
 loadPredictionData <- function(newData, covariateList.java){
   
-  xVarNames <- character(.jcall(covariateList.java, "I", "size"))
-  for(j in 1:length(xVarNames)){
-    covariate.java <- .jcast(
-      .jcall(covariateList.java, makeResponse(.class_Object), "get", as.integer(j-1)),
-      .class_Covariate
-    )
-    
-    xVarNames[j] <- .jcall(covariate.java, makeResponse(.class_String), "getName")
-  }
+  xVarNames <- extractCovariateNamesFromJavaList(covariateList.java)
   
   if(any(!(xVarNames %in% names(newData)))){
     varsMissing = xVarNames[!(xVarNames %in% names(newData))]
@@ -84,3 +76,16 @@ loadPredictionData <- function(newData, covariateList.java){
   return(rowList)
 }
 
+extractCovariateNamesFromJavaList <- function(covariateList.java){
+  xVarNames <- character(.jcall(covariateList.java, "I", "size"))
+  for(j in 1:length(xVarNames)){
+    covariate.java <- .jcast(
+      .jcall(covariateList.java, makeResponse(.class_Object), "get", as.integer(j-1)),
+      .class_Covariate
+    )
+    
+    xVarNames[j] <- .jcall(covariate.java, makeResponse(.class_String), "getName")
+  }
+  
+  return(xVarNames)
+}
diff --git a/R/misc.R b/R/misc.R
index dc4f040..6bb24e0 100644
--- a/R/misc.R
+++ b/R/misc.R
@@ -14,6 +14,23 @@ convertRListToJava <- function(lst){
   return(javaList)
 }
 
+#Internal function
+convertJavaListToR <- function(javaList, class = .class_Object){
+  lst <- list()
+  
+  javaList.length <- .jcall(javaList, "I", "size")
+  
+  for(i in 0:(javaList.length - 1)){
+    object <- .jcall(javaList, makeResponse(.class_Object), "get", as.integer(i))
+    object <- .jcast(object, class)
+    
+    lst[[i+1]] <- object
+  }
+  
+  return(lst)
+  
+}
+
 #' @export
 print.SplitFinder = function(x, ...) print(x$call)
 
diff --git a/R/processCensoringDistribution.R b/R/processCensoringDistribution.R
new file mode 100644
index 0000000..7e57048
--- /dev/null
+++ b/R/processCensoringDistribution.R
@@ -0,0 +1,39 @@
+
+
+# Internal function. Takes a censoring distribution and turns it into a
+# RightContinuousStepFunction Java object.
+processCensoringDistribution <- function(censoringDistribution){
+
+  if(is.numeric(censoringDistribution)){
+    # estimate ECDF
+    censoringTimes <- .jarray(censoringDistribution, "D")
+    java.censoringDistribution <- .jcall(.class_Utils, makeResponse(.class_RightContinuousStepFunction), "estimateOneMinusECDF", censoringTimes)
+    
+  } else if(is.list(censoringDistribution)){
+    # First check that censoringDistribution fits the correct format
+    if(is.null(censoringDistribution$x) | is.null(censoringDistribution$y)){
+      stop("If the censoringDistribution is provided as a list, it must have an x and a y item that are numeric.")
+    }
+    
+    if(length(censoringDistribution$x) != length(censoringDistribution$y)){
+      stop("x and y in censoringDistribution must have the same length.")
+    }
+    
+    if(!is.numeric(censoringDistribution$x) | !is.numeric(censoringDistribution$y)){
+      stop("x and y in censoringDistribution must both be numeric.")
+    }
+    
+    java.censoringDistribution <- createRightContinuousStepFunction(censoringDistribution$x, censoringDistribution$y, defaultY = 1.0)
+    
+  } else if("stepfun" %in% class(censoringDistribution)){
+    x <- stats::knots(censoringDistribution)
+    y <- censoringDistribution(x)
+    
+    java.censoringDistribution <- createRightContinuousStepFunction(x, y, defaultY = 1.0)
+  }
+  else{
+    stop("Invalid censoringDistribution")
+  }
+    
+  return(java.censoringDistribution)
+}
\ No newline at end of file
diff --git a/R/processFormula.R b/R/processFormula.R
new file mode 100644
index 0000000..26d1097
--- /dev/null
+++ b/R/processFormula.R
@@ -0,0 +1,59 @@
+
+# Internal function that takes a formula and processes it for use in the Java
+# code. existingCovariateList is optional; if not provided then a new one is
+# created internally.
+processFormula <- function(formula, data, covariateList.java = NULL){
+  
+  # Having an R copy of the data loaded at the same time can be wasteful; we
+  # also allow users to provide an environment of the data which gets removed
+  # after being imported into Java
+  if(class(data) == "environment"){
+    if(is.null(data$data)){
+      stop("When providing an environment with the dataset, the environment must contain an item called 'data'")
+    }
+    
+    env <- data
+    data <- env$data
+    env$data <- NULL
+    gc()
+  }
+  
+  yVar <- formula[[2]]
+  
+  responses <- NULL
+  variablesToDrop <- character(0)
+  
+  # yVar is a call object; as.character(yVar) will be the different components, including the parameters.
+  # if the length of yVar is > 1 then it's a function call. If the length is 1, and it's not in data, 
+  # then we also need to explicitly evaluate it
+  if(class(yVar) == "call" || !(as.character(yVar) %in% colnames(data))){
+    # yVar is a function like CR_Response
+    responses <- eval(expr=yVar, envir=data)
+    
+    if(class(formula[[3]]) == "name" && as.character(formula[[3]])=="."){
+      # do any of the variables match data in data? We need to track that so we can drop them later
+      variablesToDrop <- as.character(yVar)[as.character(yVar) %in% names(data)]
+    }
+    
+    formula[[2]] <- NULL
+    
+  } else if(class(yVar) == "name"){ # and implicitly yVar is contained in data
+    variablesToDrop <- as.character(yVar)
+  }
+  
+  # Includes responses which we may need to later cut out if `.` was used on the
+  # right-hand-side
+  filteredData <- stats::model.frame(formula=formula, data=data, na.action=stats::na.pass)
+  
+  if(is.null(responses)){ # If this if-statement runs then we have a simple (i.e. numeric) response
+    responses <- stats::model.response(filteredData)
+  }
+  
+  # remove any response variables on the right-hand-side
+  covariateData <- filteredData[, !(names(filteredData) %in% variablesToDrop), drop=FALSE]
+  
+  
+  dataset <- loadData(covariateData, colnames(covariateData), responses, covariateList.java = covariateList.java)
+  
+  return(dataset)
+}
\ No newline at end of file
diff --git a/R/train.R b/R/train.R
index 2cfa379..116bc09 100644
--- a/R/train.R
+++ b/R/train.R
@@ -14,7 +14,7 @@ getCores <- function(){
   return(cores)
 }
 
-train.internal <- function(responses, covariateData, splitFinder, 
+train.internal <- function(dataset, splitFinder, 
                            nodeResponseCombiner, forestResponseCombiner, ntree, 
                            numberOfSplits, mtry, nodeSize, maxNodeDepth, 
                            splitPureNodes, savePath, savePath.overwrite, 
@@ -52,15 +52,15 @@ train.internal <- function(responses, covariateData, splitFinder,
   }
   
   if(is.null(splitFinder)){
-    splitFinder <- splitFinderDefault(responses)
+    splitFinder <- splitFinderDefault(dataset$responses)
   }
   
   if(is.null(nodeResponseCombiner)){
-    nodeResponseCombiner <- nodeResponseCombinerDefault(responses)
+    nodeResponseCombiner <- nodeResponseCombinerDefault(dataset$responses)
   }
   
   if(is.null(forestResponseCombiner)){
-    forestResponseCombiner <- forestResponseCombinerDefault(responses)
+    forestResponseCombiner <- forestResponseCombinerDefault(dataset$responses)
   }
   
 
@@ -75,20 +75,6 @@ train.internal <- function(responses, covariateData, splitFinder,
     stop("forestResponseCombiner must be a ResponseCombiner")
   }
   
-  if(class(covariateData)=="environment"){
-    if(is.null(covariateData$data)){
-      stop("When providing an environment with the dataset, the environment must contain an item called 'data'")
-    }
-    dataset <- loadData(covariateData$data, colnames(covariateData$data), responses)
-    covariateData$data <- NULL # save memory, hopefully
-    gc() # explicitly try to save memory
-  }
-  else{
-    dataset <- loadData(covariateData, colnames(covariateData), responses)
-  }
-
-  
-  
   treeTrainer <- createTreeTrainer(responseCombiner=nodeResponseCombiner,
                                    splitFinder=splitFinder,
                                    covariateList=dataset$covariateList,
@@ -188,7 +174,7 @@ train.internal <- function(responses, covariateData, splitFinder,
 #'
 #' @param formula You may specify the response and covariates as a formula
 #'   instead; make sure the response in the formula is still properly
-#'   constructed; see \code{responses}
+#'   constructed.
 #' @param data A data.frame containing the columns of the predictors and
 #'   responses.
 #' @param splitFinder A split finder that's used to score splits in the random
@@ -314,74 +300,16 @@ train <- function(formula, data, splitFinder = NULL, nodeResponseCombiner = NULL
                   savePath.overwrite=c("warn", "delete", "merge"), cores = getCores(),
                   randomSeed = NULL, displayProgress = TRUE){
   
-  # Having an R copy of the data loaded at the same time can be wasteful; we
-  # also allow users to provide an environment of the data which gets removed
-  # after being imported into Java
-  env <- NULL
-  if(class(data) == "environment"){
-    if(is.null(data$data)){
-      stop("When providing an environment with the dataset, the environment must contain an item called 'data'")
-    }
-    
-    env <- data
-    data <- env$data
-  }
-
-  yVar <- formula[[2]]
-
-  responses <- NULL
-  variablesToDrop <- character(0)
+  dataset <- processFormula(formula, data)
   
-  # yVar is a call object; as.character(yVar) will be the different components, including the parameters.
-  # if the length of yVar is > 1 then it's a function call. If the length is 1, and it's not in data, 
-  # then we also need to explicitly evaluate it
-  if(class(yVar)=="call" || !(as.character(yVar) %in% colnames(data))){
-    # yVar is a function like CompetingRiskResponses
-    responses <- eval(expr=yVar, envir=data)
-    
-    if(class(formula[[3]]) == "name" && as.character(formula[[3]])=="."){
-      # do any of the variables match data in data? We need to track that so we can drop them later
-      variablesToDrop <- as.character(yVar)[as.character(yVar) %in% names(data)]
-    }
-    
-    formula[[2]] <- NULL
-
-  } else if(class(yVar)=="name"){ # and implicitly yVar is contained in data
-    variablesToDrop <- as.character(yVar)
-  }
-
-  # Includes responses which we may need to later cut out
-  mf <- stats::model.frame(formula=formula, data=data, na.action=stats::na.pass)
-
-  if(is.null(responses)){
-    responses <- stats::model.response(mf)
-  }
-
-  # remove any response variables
-  mf <- mf[,!(names(mf) %in% variablesToDrop), drop=FALSE]
-  
-  # If environment was provided instead of data
-  if(!is.null(env)){
-    env$data <- mf
-    rm(data)
-    forest <- train.internal(responses, env, splitFinder = splitFinder,
-                             nodeResponseCombiner = nodeResponseCombiner,
-                             forestResponseCombiner = forestResponseCombiner,
-                             ntree = ntree, numberOfSplits = numberOfSplits,
-                             mtry = mtry, nodeSize = nodeSize, maxNodeDepth = maxNodeDepth,
-                             splitPureNodes = splitPureNodes, savePath = savePath,
-                             savePath.overwrite = savePath.overwrite, cores = cores,
-                             randomSeed = randomSeed, displayProgress = displayProgress)
-  } else{
-    forest <- train.internal(responses, mf, splitFinder = splitFinder,
-                             nodeResponseCombiner = nodeResponseCombiner,
-                             forestResponseCombiner = forestResponseCombiner,
-                             ntree = ntree, numberOfSplits = numberOfSplits,
-                             mtry = mtry, nodeSize = nodeSize, maxNodeDepth = maxNodeDepth,
-                             splitPureNodes = splitPureNodes, savePath = savePath,
-                             savePath.overwrite = savePath.overwrite, cores = cores,
-                             randomSeed = randomSeed, displayProgress = displayProgress)
-  }
+  forest <- train.internal(dataset, splitFinder = splitFinder,
+                           nodeResponseCombiner = nodeResponseCombiner,
+                           forestResponseCombiner = forestResponseCombiner,
+                           ntree = ntree, numberOfSplits = numberOfSplits,
+                           mtry = mtry, nodeSize = nodeSize, maxNodeDepth = maxNodeDepth,
+                           splitPureNodes = splitPureNodes, savePath = savePath,
+                           savePath.overwrite = savePath.overwrite, cores = cores,
+                           randomSeed = randomSeed, displayProgress = displayProgress)
   
   forest$call <- match.call()
   forest$formula <- formula
diff --git a/R/vimp.R b/R/vimp.R
new file mode 100644
index 0000000..27211e1
--- /dev/null
+++ b/R/vimp.R
@@ -0,0 +1,175 @@
+
+
+#' Variable Importance
+#'
+#' Calculate variable importance by recording the increase in error when a given
+#' predictor is randomly permuted. Regression forests uses mean squared error;
+#' competing risks uses integrated Brier score.
+#'
+#' @param forest The forest that was trained.
+#' @param newData A test set of the data if available. If not, then out of bag
+#'   errors will be attempted on the training set.
+#' @param randomSeed The source of randomness used to permute the values. Can be
+#'   left blank.
+#' @param events If using competing risks forest, the events that the error
+#'   measure used for VIMP should be calculated on.
+#' @param time If using competing risks forest, the upper bound of the
+#'   integrated Brier score.
+#' @param censoringDistribution (Optional) If using competing risks forest, the
+#'   censoring distribution. See \code{\link{integratedBrierScore} for details.}
+#' @param eventWeights (Optional) If using competing risks forest, weights to be
+#'   applied to the error for each of the \code{events}.
+#'
+#' @return A named numeric vector of importance values.
+#' @export
+#'
+#' @examples
+#' data(wihs)
+#'
+#' forest <- train(CR_Response(status, time) ~ ., wihs,
+#'  ntree = 100, numberOfSplits = 0, mtry=3, nodeSize = 5)
+#'
+#' vimp(forest, events = 1:2, time = 8.0)
+#' 
+vimp <- function(
+  forest,
+  newData = NULL,
+  randomSeed = NULL,
+  type = c("mean", "z", "raw"),
+  events = NULL,
+  time = NULL,
+  censoringDistribution = NULL,
+  eventWeights = NULL){
+  
+  if(is.null(newData) & is.null(forest$dataset)){
+    stop("forest doesn't have a copy of the training data loaded (this happens if you just loaded it); please manually specify newData and possibly out.of.bag")
+  }
+  
+  # Basically we check if type is either null, length 0, or one of the invalid values.
+  # We can't include the last statement in the same statement as length(tyoe) < 1,
+  # because R checks both cases and a different error would display if length(type) == 0
+  typeError = is.null(type) | length(type) < 1
+  if(!typeError){
+    typeError = !(type[1] %in% c("mean", "z", "raw"))
+  }
+  if(typeError){
+    stop("A valid response type must be provided.")
+  }
+  
+  if(is.null(newData)){
+    data.java <- forest$dataset
+    out.of.bag <- TRUE
+    
+  }
+  else{ # newData is provided
+    data.java <- processFormula(forest$formula, newData, forest$covariateList)$dataset
+    out.of.bag <- FALSE
+  }
+  
+  predictionClass <- forest$params$forestResponseCombiner$outputClass
+  
+  if(predictionClass == "CompetingRiskFunctions"){
+    if(is.null(time) | length(time) != 1){
+      stop("time must be set at length 1")
+    }
+    
+    errorCalculator.java <- ibsCalculatorWrapper(
+      events = events,
+      time = time,
+      censoringDistribution = censoringDistribution,
+      eventWeights = eventWeights)
+    
+  } else if(predictionClass == "numeric"){
+    errorCalculator.java <- .jnew(.class_RegressionErrorCalculator)
+    errorCalculator.java <- .jcast(errorCalculator.java, .class_ErrorCalculator)
+    
+  } else{
+    stop(paste0("VIMP not yet supported for ", predictionClass, ". If you're just using a non-custom version of largeRCRF then this is a bug and should be reported."))
+    
+  }
+  
+  forest.trees.java <- .jcall(forest$javaObject, makeResponse(.class_List), "getTrees")
+  
+  vimp.calculator <- .jnew(.class_VariableImportanceCalculator, 
+                           errorCalculator.java, 
+                           forest.trees.java,
+                           data.java,
+                           out.of.bag # isTrainingSet parameter
+                           )
+  
+  random.java <- NULL
+  if(!is.null(randomSeed)){
+    random.java <- .jnew(.class_Random, .jlong(as.integer(randomSeed)))
+  }
+  random.java <- .object_Optional(random.java)
+  
+  covariateRList <- convertJavaListToR(forest$covariateList, class = .class_Covariate)
+  importanceValues <- matrix(nrow = forest$params$ntree, ncol = length(covariateRList))
+  colnames(importanceValues) <- extractCovariateNamesFromJavaList(forest$covariateList)
+  
+  for(j in 1:length(covariateRList)){
+    covariateJava <- covariateRList[[j]]
+    covariateJava <- 
+    
+    importanceValues[, j] <- .jcall(vimp.calculator, "[D", "calculateVariableImportanceRaw", covariateJava, random.java)
+  }
+  
+  if(type[1] == "raw"){
+    return(importanceValues)
+  } else if(type[1] == "mean"){
+    meanImportanceValues <- apply(importanceValues, 2, mean)
+    return(meanImportanceValues)
+  } else if(type[1] == "z"){
+    zImportanceValues <- apply(importanceValues, 2, function(x){
+      meanValue <- mean(x)
+      standardError <- sd(x)/sqrt(length(x))
+      return(meanValue / standardError)
+    })
+    return(zImportanceValues)
+    
+  } else{
+    stop("A valid response type must be provided.")
+  }
+
+  
+  return(importance)
+  
+}
+
+# Internal function
+ibsCalculatorWrapper <- function(events, time, censoringDistribution = NULL, eventWeights = NULL){
+  if(is.null(events)){
+    stop("events must be specified if using vimp on competing risks data")
+  }
+  
+  if(is.null(time)){
+    stop("time must be specified if using vimp on competing risks data")
+  }
+  
+  
+  java.censoringDistribution <- NULL
+  if(!is.null(censoringDistribution)){
+    java.censoringDistribution <- processCensoringDistribution(censoringDistribution)
+    java.censoringDistribution <- .object_Optional(java.censoringDistribution)
+  }
+  else{
+    java.censoringDistribution <- .object_Optional(NULL)
+  }
+  
+  ibsCalculator.java <- .jnew(.class_IBSCalculator, java.censoringDistribution)
+  
+  if(is.null(eventWeights)){
+    eventWeights <- rep(1, times = length(events))
+  }
+  
+  ibsCalculatorWrapper.java <- .jnew(.class_IBSErrorCalculatorWrapper, 
+                                     ibsCalculator.java,
+                                     .jarray(as.integer(events)),
+                                     as.numeric(time),
+                                     .jarray(as.numeric(eventWeights)))
+  
+  ibsCalculatorWrapper.java <- .jcast(ibsCalculatorWrapper.java, .class_ErrorCalculator)
+  return(ibsCalculatorWrapper.java)
+  
+  
+}
\ No newline at end of file
diff --git a/inst/java/largeRCRF-library-1.0-SNAPSHOT.jar b/inst/java/largeRCRF-library-1.0-SNAPSHOT.jar
index f7ce8af..ad8f858 100644
Binary files a/inst/java/largeRCRF-library-1.0-SNAPSHOT.jar and b/inst/java/largeRCRF-library-1.0-SNAPSHOT.jar differ
diff --git a/man/train.Rd b/man/train.Rd
index faa2542..a07e47c 100644
--- a/man/train.Rd
+++ b/man/train.Rd
@@ -13,7 +13,7 @@ train(formula, data, splitFinder = NULL, nodeResponseCombiner = NULL,
 \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; see \code{responses}}
+constructed.}
 
 \item{data}{A data.frame containing the columns of the predictors and
 responses.}
diff --git a/man/vimp.Rd b/man/vimp.Rd
new file mode 100644
index 0000000..21ce486
--- /dev/null
+++ b/man/vimp.Rd
@@ -0,0 +1,48 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/vimp.R
+\name{vimp}
+\alias{vimp}
+\title{Variable Importance}
+\usage{
+vimp(forest, newData = NULL, randomSeed = NULL, type = c("mean", "z",
+  "raw"), events = NULL, time = NULL, censoringDistribution = NULL,
+  eventWeights = NULL)
+}
+\arguments{
+\item{forest}{The forest that was trained.}
+
+\item{newData}{A test set of the data if available. If not, then out of bag
+errors will be attempted on the training set.}
+
+\item{randomSeed}{The source of randomness used to permute the values. Can be
+left blank.}
+
+\item{events}{If using competing risks forest, the events that the error
+measure used for VIMP should be calculated on.}
+
+\item{time}{If using competing risks forest, the upper bound of the
+integrated Brier score.}
+
+\item{censoringDistribution}{(Optional) If using competing risks forest, the
+censoring distribution. See \code{\link{integratedBrierScore} for details.}}
+
+\item{eventWeights}{(Optional) If using competing risks forest, weights to be
+applied to the error for each of the \code{events}.}
+}
+\value{
+A named numeric vector of importance values.
+}
+\description{
+Calculate variable importance by recording the increase in error when a given
+predictor is randomly permuted. Regression forests uses mean squared error;
+competing risks uses integrated Brier score.
+}
+\examples{
+data(wihs)
+
+forest <- train(CR_Response(status, time) ~ ., wihs,
+ ntree = 100, numberOfSplits = 0, mtry=3, nodeSize = 5)
+
+vimp(forest, events = 1:2, time = 8.0)
+
+}
diff --git a/tests/testthat/test_vimp.R b/tests/testthat/test_vimp.R
new file mode 100644
index 0000000..b6115d5
--- /dev/null
+++ b/tests/testthat/test_vimp.R
@@ -0,0 +1,102 @@
+context("Use VIMP without error")
+
+test_that("VIMP doesn't crash; no test dataset", {
+
+  data(wihs)
+  
+  forest <- train(CR_Response(status, time) ~ ., wihs, ntree=50, numberOfSplits=0, mtry=1, nodeSize=5, displayProgress=FALSE)
+  
+  # Run VIMP several times under different scenarios
+  importance <- vimp(forest, type="raw", events=1:2, time=5.0)
+  vimp(forest, type="raw", events=1, time=5.0)
+  vimp(forest, type="raw", events=1:2, time=5.0, eventWeights = c(0.2, 0.8))
+  
+  # Not much of a test, but the Java code tests more for correctness. This just
+  # tests that the R code runs without error.
+  expect_equal(ncol(importance), 4) # 4 predictors
+  
+})
+
+
+test_that("VIMP doesn't crash; test dataset", {
+  
+  data(wihs)
+  
+  trainingData <- wihs[1:1000,]
+  testData <- wihs[1001:nrow(wihs),]
+  
+  forest <- train(CR_Response(status, time) ~ ., trainingData, ntree=50, numberOfSplits=0, mtry=1, nodeSize=5, displayProgress=FALSE, cores=1)
+  
+  # Run VIMP several times under different scenarios
+  importance <- vimp(forest, newData=testData, type="raw", events=1:2, time=5.0)
+  vimp(forest, newData=testData, type="raw", events=1, time=5.0)
+  vimp(forest, newData=testData, type="raw", events=1:2, time=5.0, eventWeights = c(0.2, 0.8))
+  
+  # Not much of a test, but the Java code tests more for correctness. This just
+  # tests that the R code runs without error.
+  expect_equal(ncol(importance), 4) # 4 predictors
+  
+})
+
+
+test_that("VIMP doesn't crash; censoring distribution; all methods equal", {
+  
+  sampleData <- data.frame(x=rnorm(100))
+  sampleData$T <- sample(0:4, size=100, replace = TRUE) # the censor distribution we provide needs to conform to the data or we can get NaNs
+  sampleData$delta <- sample(0:2, size = 100, replace = TRUE)
+  
+  testData <- sampleData[1:5,]
+  trainingData <- sampleData[6:100,]
+  
+  forest <- train(CR_Response(delta, T) ~ x, trainingData, ntree=50, numberOfSplits=0, mtry=1, nodeSize=5, cores=2, displayProgress=FALSE)
+  
+  importance1 <- vimp(forest, type="raw", events=1:2, time=4.0, randomSeed=50, 
+                      censoringDistribution = c(0,1,1,2,3,4))
+  importance2 <- vimp(forest, type="raw", events=1:2, time=4.0, randomSeed=50, 
+                      censoringDistribution = list(x = 0:4, y = 1 - c(1/6, 3/6, 4/6, 5/6, 6/6)))
+  importance3 <- vimp(forest, type="raw", events=1:2, time=4.0, randomSeed=50, 
+                      censoringDistribution = stepfun(x=0:4, y=1 - c(0, 1/6, 3/6, 4/6, 5/6, 6/6)))
+  
+  expect_equal(importance1, importance2)
+  expect_equal(importance1, importance3)
+  
+})
+
+test_that("VIMP doesn't crash; regression dataset", {
+  
+  data <- data.frame(x1=rnorm(1000), x2=rnorm(1000), x3=rnorm(1000))
+  data$y <- data$x1 + 3*data$x2 + 0.05*data$x3 + rnorm(1000)
+  
+  forest <- train(y ~ ., data, ntree=50, numberOfSplits=100, mtry=2, nodeSize=5, displayProgress=FALSE)
+  
+  importance <- vimp(forest, type="mean")
+  
+  expect_true(importance["x2"] > importance["x3"])
+  
+  # Not much of a test, but the Java code tests more for correctness. This just
+  # tests that the R code runs without error.
+  expect_equal(length(importance), 3) # 3 predictors
+  
+})
+
+test_that("VIMP produces mean and z scores correctly", {
+  
+  data <- data.frame(x1=rnorm(1000), x2=rnorm(1000), x3=rnorm(1000))
+  data$y <- data$x1 + 3*data$x2 + 0.05*data$x3 + rnorm(1000)
+  
+  forest <- train(y ~ ., data, ntree=50, numberOfSplits=100, mtry=2, nodeSize=5, displayProgress=FALSE)
+  
+  actual.importance.raw <- vimp(forest, type="raw", randomSeed=5)
+  actual.importance.mean <- vimp(forest, type="mean", randomSeed=5)
+  actual.importance.z <- vimp(forest, type="z", randomSeed=5)
+  
+  expected.importance.mean <- apply(actual.importance.raw, 2, mean)
+  expected.importance.z <- apply(actual.importance.raw, 2, function(x){
+    mn <- mean(x)
+    return( mn / (sd(x) / sqrt(length(x))) )
+  })
+  
+  expect_equal(expected.importance.mean, actual.importance.mean)
+  expect_equal(expected.importance.z, actual.importance.z)
+  
+})
\ No newline at end of file