title: MLlib: How does RFormula.fit() work?
body: <p>One possibility to create a model with Spark's <code>MLlib</code> is the <code>RFormula</code> module from <code>pyspark.ml.feature</code> as explained in the <a href="https://spark.apache.org/docs/latest/ml-features.html#rformula" rel="nofollow noreferrer">docs</a>. However, I can't find any explanation how <code>fit</code> is actually implemented in this case. Does it use a squared loss function or something else? Where can I find this kind of information? The <a href="https://spark.apache.org/docs/latest/api/python/_modules/pyspark/ml/feature.html#RFormula" rel="nofollow noreferrer">source</a> is really hard to understand...</p>