Github user felixcheung commented on a diff in the pull request: https://github.com/apache/spark/pull/15365#discussion_r83122799 --- Diff: R/pkg/R/mllib.R --- @@ -647,6 +654,195 @@ setMethod("predict", signature(object = "KMeansModel"), predict_internal(object, newData) }) +#' Logistic Regression Model +#' +#' Fits an logistic regression model against a Spark DataFrame. It supports "binomial": Binary logistic regression +#' with pivoting; "multinomial": Multinomial logistic (softmax) regression without pivoting, similar to glmnet. +#' Users can print, make predictions on the produced model and save the model to the input path. +#' +#' @param data SparkDataFrame for training +#' @param formula A symbolic description of the model to be fitted. Currently only a few formula +#' operators are supported, including '~', '.', ':', '+', and '-'. +#' @param regParam the regularization parameter. Default is 0.0. +#' @param elasticNetParam the ElasticNet mixing parameter. For alpha = 0, the penalty is an L2 penalty. +#' For alpha = 1, it is an L1 penalty. For 0 < alpha < 1, the penalty is a combination +#' of L1 and L2. Default is 0.0 which is an L2 penalty. +#' @param maxIter maximum iteration number. +#' @param tol convergence tolerance of iterations. +#' @param fitIntercept whether to fit an intercept term. Default is TRUE. +#' @param family the name of family which is a description of the label distribution to be used in the model. +#' Supported options: +#' - "auto": Automatically select the family based on the number of classes: +#' If numClasses == 1 || numClasses == 2, set to "binomial". +#' Else, set to "multinomial". +#' - "binomial": Binary logistic regression with pivoting. +#' - "multinomial": Multinomial logistic (softmax) regression without pivoting. +#' Default is "auto". +#' @param standardization whether to standardize the training features before fitting the model. The coefficients +#' of models will be always returned on the original scale, so it will be transparent for +#' users. Note that with/without standardization, the models should be always converged +#' to the same solution when no regularization is applied. Default is TRUE, same as glmnet. +#' @param threshold in binary classification, in range [0, 1]. If the estimated probability of class label 1 +#' is > threshold, then predict 1, else 0. A high threshold encourages the model to predict 0 +#' more often; a low threshold encourages the model to predict 1 more often. Note: Setting this with +#' threshold p is equivalent to setting thresholds (Array(1-p, p)). When threshold is set, any user-set +#' value for thresholds will be cleared. If both threshold and thresholds are set, then they must be +#' equivalent. Default is 0.5. +#' @param thresholds in multiclass (or binary) classification to adjust the probability of predicting each class. +#' Array must have length equal to the number of classes, with values > 0, excepting that at most one +#' value may be 0. The class with largest value p/t is predicted, where p is the original probability +#' of that class and t is the class's threshold. Note: When thresholds is set, any user-set +#' value for threshold will be cleared. If both threshold and thresholds are set, then they must be +#' equivalent. Default is NULL. +#' @param weightCol The weight column name. +#' @param aggregationDepth depth for treeAggregate (>= 2). If the dimensions of features or the number of partitions +#' are large, this param could be adjusted to a larger size. Default is 2. +#' @param ... additional arguments passed to the method. +#' @return \code{spark.logit} returns a fitted logistic regression model +#' @rdname spark.logit +#' @aliases spark.logit,SparkDataFrame,formula-method +#' @name spark.logit +#' @export +#' @examples +#' \dontrun{ +#' sparkR.session() +#' # binary logistic regression +#' label <- c(1.0, 1.0, 1.0, 0.0, 0.0) +#' feature <- c(1.1419053, 0.9194079, -0.9498666, -1.1069903, 0.2809776) +#' binary_data <- as.data.frame(cbind(label, feature)) +#' binary_df <- suppressWarnings(createDataFrame(binary_data)) +#' blr_model <- spark.logit(binary_df, label ~ feature, threshold = 1.0) +#' blr_predict <- collect(select(predict(blr_model, binary_df), "prediction")) +#' +#' # summary of binary logistic regression +#' blr_summary <- summary(blr_model) +#' blr_fmeasure <- collect(select(blr_summary$fMeasureByThreshold, "threshold", "F-Measure")) +#' # save fitted model to input path +#' path <- "path/to/model" +#' write.ml(blr_model, path) +#' +#' # can also read back the saved model and print +#' savedModel <- read.ml(path) +#' summary(savedModel) +#' +#' # multinomial logistic regression +#' +#' label <- c(0.0, 1.0, 2.0, 0.0, 0.0) +#' feature1 <- c(4.845940, 5.64480, 7.430381, 6.464263, 5.555667) +#' feature2 <- c(2.941319, 2.614812, 2.162451, 3.339474, 2.970987) +#' feature3 <- c(1.322733, 1.348044, 3.861237, 9.686976, 3.447130) +#' feature4 <- c(1.3246388, 0.5510444, 0.9225810, 1.2147881, 1.6020842) +#' data <- as.data.frame(cbind(label, feature1, feature2, feature3, feature4)) +#' df <- suppressWarnings(createDataFrame(data)) +#' +#' model <- spark.logit(df, label ~ ., family = "multinomial", thresholds=c(0, 1, 1)) +#' predict1 <- collect(select(predict(model, df), "prediction")) +#' } +#' @note spark.logit since 2.1.0 +setMethod("spark.logit", signature(data = "SparkDataFrame", formula = "formula"), + function(data, formula, regParam = 0.0, elasticNetParam = 0.0, maxIter = 100, + tol = 1E-6, fitIntercept = TRUE, family = "auto", standardization = TRUE, + threshold = 0.5, thresholds = NULL, weightCol = NULL, aggregationDepth = 2) { --- End diff -- perhaps turning that into a list/array on the Scala side so it becomes list on the R side?

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