Feature Transformation -- Discrete Cosine Transform (DCT) (Transformer)

A feature transformer that takes the 1D discrete cosine transform of a real vector. No zero padding is performed on the input vector. It returns a real vector of the same length representing the DCT. The return vector is scaled such that the transform matrix is unitary (aka scaled DCT-II).

ft_dct(x, input_col = NULL, output_col = NULL, inverse = FALSE,
  uid = random_string("dct_"), ...)

ft_discrete_cosine_transform(x, input_col, output_col, inverse = FALSE,
  uid = random_string("dct_"), ...)



A spark_connection, ml_pipeline, or a tbl_spark.


The name of the input column.


The name of the output column.


Indicates whether to perform the inverse DCT (TRUE) or forward DCT (FALSE).


A character string used to uniquely identify the feature transformer.


Optional arguments; currently unused.


The object returned depends on the class of x.

  • spark_connection: When x is a spark_connection, the function returns a ml_transformer, a ml_estimator, or one of their subclasses. The object contains a pointer to a Spark Transformer or Estimator object and can be used to compose Pipeline objects.

  • ml_pipeline: When x is a ml_pipeline, the function returns a ml_pipeline with the transformer or estimator appended to the pipeline.

  • tbl_spark: When x is a tbl_spark, a transformer is constructed then immediately applied to the input tbl_spark, returning a tbl_spark


ft_discrete_cosine_transform() is an alias for ft_dct for backwards compatibility.

See also