Combine multiple vectors into a single row-vector; that is, where each row element of the newly generated column is a vector formed by concatenating each row element from the specified input columns.
ft_vector_assembler(x, input.col = NULL, output.col = NULL, ...)An object (usually a spark_tbl) coercable to a Spark DataFrame.
The name of the input column(s).
The name of the output column.
Optional arguments; currently unused.
See http://spark.apache.org/docs/latest/ml-features.html for more information on the set of transformations available for DataFrame columns in Spark.
Other feature transformation routines: ft_binarizer,
  ft_bucketizer,
  ft_count_vectorizer,
  ft_discrete_cosine_transform,
  ft_elementwise_product,
  ft_index_to_string,
  ft_one_hot_encoder,
  ft_quantile_discretizer,
  ft_regex_tokenizer,
  ft_sql_transformer,
  ft_string_indexer,
  ft_tokenizer, sdf_mutate