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Diffstat (limited to 'mllib')
| -rw-r--r-- | mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala index 6cc9d02544..c21da218b3 100644 --- a/mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala +++ b/mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala @@ -45,6 +45,27 @@ private[feature] trait RFormulaBase extends HasFeaturesCol with HasLabelCol { * Implements the transforms required for fitting a dataset against an R model formula. Currently * we support a limited subset of the R operators, including '~', '.', ':', '+', and '-'. Also see * the R formula docs here: http://stat.ethz.ch/R-manual/R-patched/library/stats/html/formula.html + * + * The basic operators are: + * - `~` separate target and terms + * - `+` concat terms, "+ 0" means removing intercept + * - `-` remove a term, "- 1" means removing intercept + * - `:` interaction (multiplication for numeric values, or binarized categorical values) + * - `.` all columns except target + * + * Suppose `a` and `b` are double columns, we use the following simple examples + * to illustrate the effect of `RFormula`: + * - `y ~ a + b` means model `y ~ w0 + w1 * a + w2 * b` where `w0` is the intercept and `w1, w2` + * are coefficients. + * - `y ~ a + b + a:b - 1` means model `y ~ w1 * a + w2 * b + w3 * a * b` where `w1, w2, w3` + * are coefficients. + * + * RFormula produces a vector column of features and a double or string column of label. + * Like when formulas are used in R for linear regression, string input columns will be one-hot + * encoded, and numeric columns will be cast to doubles. + * If the label column is of type string, it will be first transformed to double with + * `StringIndexer`. If the label column does not exist in the DataFrame, the output label column + * will be created from the specified response variable in the formula. */ @Experimental class RFormula(override val uid: String) extends Estimator[RFormulaModel] with RFormulaBase { |