R/TADrandomForest.R

In preciseTAD: preciseTAD: A machine learning framework for precise TAD boundary prediction

#' A wrapper function passed to \code{caret::train} to apply a random forest
#' classification algorithm built and tested on user-defined binned domain
#' data from \code{\link{createTADdata}}.
#'
#' @param trainData Data frame, the binned data matrix to built a random forest
#' classifiers (can be obtained using \code{\link{createTADdata}}). Required.
#' @param testData Data frame, the binned data matrix to test random forest
#' classifiers (can be obtained using \code{\link{createTADdata}}). The first
#' column must be a factor with positive class "Yes". Default is NULL in which
#' case no performances are evaluated.
#' @param tuneParams List, providing \code{mtry}, \code{ntree}, and
#' \code{nodesize} parameters to feed into \code{\link{randomForest}}. Default
#' is list(mtry = ceiling(sqrt(ncol(trainData) - 1)), ntree = 500,
#' nodesize = 1). If multiple values are provided, then a grid search is
#' performed to tune the model. Required.
#' @param cvFolds Numeric, number of k-fold cross-validation to perform in
#' order to tune the hyperparameters. Required.
#' @param cvMetric Character, performance metric to use to choose optimal
#' tuning parameters (one of either "Kappa", "Accuracy", "MCC", "ROC", "Sens",
#' "Spec", "Pos Pred Value", "Neg Pred Value"). Default is "Accuracy".
#' @param verbose Logical, controls whether or not details regarding modeling
#' should be printed out. Default is TRUE.
#' @param model Logical, whether to keep the model object. Default is TRUE.
#' @param importances Logical, whether to extract variable importances. Default
#' is TRUE.
#' @param impMeasure Character, indicates the variable importance measure to
#' use (one of either "MDA" (mean decrease in accuracy) or "MDG" (mean decrease
#' in gini)). Ignored if importances = FALSE.
#' @param performances Logical, indicates whether various performance metrics
#' should be extracted when validating the model on the test data. Ignored if
#' testData = NULL.
#'
#' @return A list containing: 1) a train object from \code{caret} with model
#' information, 2) a data.frame of variable importance for each feature
#' included in the model, and 3) a data.frame of various performance metrics
#' @export
#'
#' @importFrom ModelMetrics mcc
#' @importFrom PRROC pr.curve
#' @importFrom pROC roc
#' @importFrom pROC auc
#' @importFrom stats predict
#' @import randomForest caret e1071
#'
#' @examples
#' # Read in ARROWHEAD-called TADs at 5kb
#' data(arrowhead_gm12878_5kb)
#'
#' # Extract unique boundaries
#' bounds.GR <- extractBoundaries(domains.mat = arrowhead_gm12878_5kb,
#'                                preprocess = FALSE,
#'                                CHR = c("CHR21", "CHR22"),
#'                                resolution = 5000)
#'
#' # Read in GRangesList of 26 TFBS
#' data(tfbsList)
#'
#' # Create the binned data matrix for CHR1 (training) and CHR22 (testing)
#' # using 5 kb binning, distance-type predictors from 26 different TFBS from
#' # the GM12878 cell line, and random under-sampling
#' tadData <- createTADdata(bounds.GR = bounds.GR,
#'                          resolution = 5000,
#'                          genomicElements.GR = tfbsList,
#'                          featureType = "distance",
#'                          resampling = "rus",
#'                          trainCHR = "CHR21",
#'                          predictCHR = "CHR22")
#'
#' # Perform random forest using TADrandomForest by tuning mtry over 10 values
#' # using 3-fold CV
#' tadModel <- TADrandomForest(trainData = tadData[[1]],
#'                             testData = tadData[[2]],
#'                             tuneParams = list(mtry = c(2,5,8,10,13,16,18,21,24,26),
#'                                             ntree = 500,
#'                                             nodesize = 1),
#'                             cvFolds = 3,
#'                             cvMetric = "Accuracy",
#'                             verbose = TRUE,
#'                             model = TRUE,
#'                             importances = TRUE,
#'                             impMeasure = "MDA",
#'                             performances = TRUE)
TADrandomForest <- function(trainData,
                            testData = NULL,
                            tuneParams = list(mtry = ceiling(sqrt(ncol(trainData)-1)),
                                              ntree = 500,
                                              nodesize = 1),
                            cvFolds = 3,
                            cvMetric = "Accuracy",
                            verbose = FALSE,
                            model = TRUE,
                            importances = TRUE,
                            impMeasure = "MDA",
                            performances = FALSE){

    #################################
    #PREDICTING TAD BOUNDARY REGIONS#
    #################################

    ########################################################################
    #Establishing summary function to evaluate cross validation performance#
    ########################################################################

    predictiveValues <- function (data, lev = NULL, model = NULL,...){
        PPVobj <- posPredValue(data[, "pred"], data[, "obs"])
        NPVobj <- negPredValue(data[, "pred"], data[, "obs"])
        out <- c(PPVobj, NPVobj)
        #out <- c(NPVobj)
        names(out) <- c("Pos Pred Value", "Neg Pred Value")
        #names(out) <- c("Neg Pred Value")
        out}

    allSummary <- function(data, lev = NULL, model = NULL){
        lvls <- levels(data$obs)

        #mcc
        mcc <- mcc(ifelse(data$obs == lev[2], 0, 1), data[, lvls[1]], cutoff = .5)

        #roc
        b1 <- twoClassSummary(data, lev, model)

        #auprc & f1
        #c1 <- prSummary(data, lev, model)

        #ppv & npv
        d1 <- predictiveValues(data, lev, model)

        #accuracy & kappa
        e1 <- defaultSummary(data, lev, model)

        out <- c(mcc, b1, d1, e1)
        names(out)[1] <- c("MCC")
        out
    }

    ########################################
    #Establishing random forest using caret#
    ########################################

    customRF <- getModelInfo(model = "rf", regex = FALSE)
    customRF$rf$parameters <- data.frame(parameter = c("mtry", "ntree", "nodesize"),
                                         class = rep("numeric", 3),
                                         label = c("mtry", "ntree", "nodesize"))
    customRF$rf$grid <- function(x, y, len = NULL, search = "grid") {}
    customRF$rf$fit <- function(x, y, wts, param, lev, last, weights, classProbs, ...) {
        randomForest(x,
                     y,
                     mtry = param$mtry,
                     ntree=param$ntree,
                     nodesize = param$nodesize,
                     importance=TRUE,
                     ...)
    }

    ##########################
    #Establishing tuning grid#
    ##########################

    tunegrid <- expand.grid(mtry = tuneParams[[1]],
                            ntree = tuneParams[[2]],
                            nodesize = tuneParams[[3]])

    ###############################
    #Establishing control function#
    ###############################

    seeds <- vector(mode = "list", length = (cvFolds+1))
    for(i in seq_len(cvFolds)) {
        seeds[[i]] <- sample.int(n=100000, nrow(tunegrid))
    }
    #for the last model
    seeds[[cvFolds+1]] <- sample.int(100000, 1)

    control <- trainControl(seeds = seeds,
                            method = "cv",
                            number = cvFolds,
                            verboseIter = ifelse(verbose == TRUE, TRUE, FALSE),
                            ## Estimate class probabilities
                            classProbs = TRUE,
                            ## Evaluate performance using
                            ## the following function
                            summaryFunction = allSummary,
                            allowParallel = FALSE)



    tadModel <- train(y~.,
                      data = trainData,
                      method = customRF$rf,
                      metric = cvMetric,
                      tuneGrid = tunegrid,
                      trControl = control)

    #####################################
    #EXTRACTING IMPORTANCES/COEFFICIENTS#
    #####################################

    if(impMeasure == "MDA") {
        rfimpvars <- data.frame(Feature=rownames(randomForest::importance(tadModel$finalModel, scale = TRUE)),
                                Importance=as.vector(randomForest::importance(tadModel$finalModel, scale = TRUE)[,3]))
        rfimpvars <- rfimpvars[order(rfimpvars$Importance, decreasing = TRUE),]
    }else if(impMeasure == "MDG") {
        rfimpvars <- data.frame(Feature=rownames(randomForest::importance(tadModel$finalModel, scale = TRUE)),
                                Importance = as.vector(randomForest::importance(tadModel$finalModel, scale = TRUE)[,4]))
        rfimpvars <- rfimpvars[order(rfimpvars$Importance, decreasing = TRUE),]
    }else {
        rfimpvars <- NA
    }

    #################################
    #EVALUATING PERFORMANCES        #
    #################################

    if(!(is.null(testData)) & performances == TRUE){
        rfperf <- data.frame(Metric = c("TN",
                                        "FN",
                                        "FP",
                                        "TP",
                                        "Total",
                                        "Sensitivity",
                                        "Specificity",
                                        "Kappa",
                                        "Accuracy",
                                        "BalancedAccuracy",
                                        "Precision",
                                        "FPR",
                                        "FNR",
                                        "NPV",
                                        "MCC",
                                        "F1",
                                        "AUC",
                                        "Youden",
                                        "AUPRC"),
                             Performance = NA)

        pred.tadModel <- as.vector(predict(tadModel,
                                           newdata=testData[,-1],
                                           type = "prob")[,"Yes"])

        fg <- pred.tadModel[testData$y == "Yes"]
        bg <- pred.tadModel[testData$y == "No"]
        pr <- pr.curve(scores.class0 = fg, scores.class1 = bg, curve = TRUE)

        pred.tadModel2 <- predict(tadModel,
                                  newdata = testData[,-1],
                                  type = "raw")


        confMat <- caret::confusionMatrix(data=pred.tadModel2, testData[,1], positive="Yes")
        TN <- as.numeric(confMat$table[1,1])
        FN <- as.numeric(confMat$table[1,2])
        FP <- as.numeric(confMat$table[2,1])
        TP <- as.numeric(confMat$table[2,2])
        rfperf[1,2] <- TN
        rfperf[2,2] <- FN
        rfperf[3,2] <- FP
        rfperf[4,2] <- TP
        rfperf[5,2] <- sum(confMat$table)
        rfperf[6,2] <- as.vector(confMat$byClass["Sensitivity"])
        rfperf[7,2] <- as.vector(confMat$byClass["Specificity"])
        rfperf[8,2] <- as.vector(confMat$overall["Kappa"])
        rfperf[9,2] <- as.vector(confMat$overall["Accuracy"])
        rfperf[10,2] <- ((TP/(TP+FN)) + (TN/(FP+TN)))/2
        rfperf[11,2] <- TP/(TP+FP)
        rfperf[12,2] <- FP/(FP+TN)
        rfperf[13,2] <- FN/(FN+TN)
        rfperf[14,2] <- TN/(TN+FN)
        rfperf[15,2] <- (TP*TN - FP*FN)/( sqrt( (TP+FP)*(TP+FN)*(TN+FP)*(TN+FN) ) )
        rfperf[16,2] <- (2*(TP/(TP+FN))*(TP/(TP+FP)))/((TP/(TP+FN)) + ((TP/(TP+FP))))
        rfperf[17,2] <- pROC::auc(pROC::roc(testData$y, pred.tadModel, quiet = TRUE))
        rfperf[18,2] <- (TP/(TP + FN)) + (TN/(TN + FP)) - 1
        rfperf[19,2] <- pr$auc.integral
    }

    results_list <- list()

    if(model == TRUE){results_list[[1]] <- tadModel}else{results_list[[1]] <- NA}
    if(importances == TRUE){results_list[[2]] <- rfimpvars}else{results_list[[2]] <- NA}
    if(!(is.null(testData)) & performances == TRUE){results_list[[3]] <- rfperf}else{results_list[[3]] <- NA}

    return(results_list)
}