Github user BenFradet commented on a diff in the pull request:
https://github.com/apache/spark/pull/10222#discussion_r47506815
--- Diff: docs/ml-features.md ---
@@ -2036,7 +2036,25 @@ System.out.println(output.select("userFeatures",
"features").first());
## RFormula
-`RFormula` selects columns specified by an [R model
formula](https://stat.ethz.ch/R-manual/R-devel/library/stats/html/formula.html).
It produces a vector column of features and a double column of labels. 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 not already
present in the DataFrame, the output label column will be created from the
specified response variable in the formula.
+`RFormula` selects columns specified by an [R model
formula](https://stat.ethz.ch/R-manual/R-devel/library/stats/html/formula.html).
+Currently we support a limited subset of the R operators, including '~',
'.', ':', '+', and '-'.
+The meanings of basic operator are:
+
+* `~` separate target and terms
+* `+` concat terms, â+ 0â means removing intercept
+* `-` remove a term, â- 1â 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, which is the same as `y ~ (a + b)^2 + 0`
+
+`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 string type, it will be first transformed to double
label with `StringIndexer`.
--- End diff --
I'd say: "If the label column is of type string, it will be first
transformed to double with `StringIndexer`."
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
