Github user felixcheung commented on a diff in the pull request:
https://github.com/apache/spark/pull/15365#discussion_r84999720
--- Diff: R/pkg/R/mllib.R ---
@@ -647,6 +654,173 @@ 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:
+#' \itemize{
+#' \item{"auto": Automatically select the family based
on the number of classes:
+#' If numClasses == 1 || numClasses == 2, set to
"binomial".
+#' Else, set to "multinomial".}
+#' \item{"binomial": Binary logistic regression with
pivoting.}
+#' \item{"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 thresholds 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 c(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. 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 0.5.
+#' @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 probabilityCol column name for predicted class conditional
probabilities. Default is "probability".
+#' @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 <- 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,
+ thresholds = 0.5, weightCol = NULL, aggregationDepth =
2,
+ probabilityCol = "probability") {
+ formula <- paste0(deparse(formula), collapse = "")
+
+ if (is.null(weightCol)) {
+ weightCol <- ""
+ }
+
+ jobj <-
callJStatic("org.apache.spark.ml.r.LogisticRegressionWrapper", "fit",
+ data@sdf, formula, as.numeric(regParam),
+ as.numeric(elasticNetParam),
as.integer(maxIter),
+ as.numeric(tol), as.logical(fitIntercept),
+ as.character(family),
as.logical(standardization),
+ as.array(thresholds),
as.character(weightCol),
+ as.integer(aggregationDepth),
as.character(probabilityCol))
+ new("LogisticRegressionModel", jobj = jobj)
+ })
+
+# Predicted values based on an LogisticRegressionModel model
+
+#' @param newData a SparkDataFrame for testing.
+#' @return \code{predict} returns the predicted values based on an
LogisticRegressionModel.
+#' @rdname spark.logit
+#' @aliases predict,LogisticRegressionModel,SparkDataFrame-method
+#' @export
+#' @note predict(LogisticRegressionModel) since 2.1.0
+setMethod("predict", signature(object = "LogisticRegressionModel"),
+ function(object, newData) {
+ predict_internal(object, newData)
+ })
+
+# Get the summary of an LogisticRegressionModel
+
+#' @param object an LogisticRegressionModel fitted by \code{spark.logit}
+#' @return \code{summary} returns the Binary Logistic regression results
of a given model as lists. Note that
+#' Multinomial logistic regression summary is not
available now.
+#' @rdname spark.logit
+#' @aliases spark.logit,SparkDataFrame,formula-method
--- End diff --
this is the `summary` method, not `spark.logit` method?
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