Perform Weighted Random Sampling on a Spark DataFrame
R/sdf_interface.R
sdf_weighted_sample
Description
Draw a random sample of rows (with or without replacement) from a Spark DataFrame If the sampling is done without replacement, then it will be conceptually equivalent to an iterative process such that in each step the probability of adding a row to the sample set is equal to its weight divided by summation of weights of all rows that are not in the sample set yet in that step.
Usage
sdf_weighted_sample(x, weight_col, k, replacement = TRUE, seed = NULL) Arguments
| Arguments | Description |
|---|---|
| x | An object coercable to a Spark DataFrame. |
| weight_col | Name of the weight column |
| k | Sample set size |
| replacement | Whether to sample with replacement |
| seed | An (optional) integer seed |
Section
Transforming Spark DataFrames
The family of functions prefixed with sdf_ generally access the Scala Spark DataFrame API directly, as opposed to the dplyr interface which uses Spark SQL. These functions will ‘force’ any pending SQL in a dplyr pipeline, such that the resulting tbl_spark object returned will no longer have the attached ‘lazy’ SQL operations. Note that the underlying Spark DataFrame does execute its operations lazily, so that even though the pending set of operations (currently) are not exposed at the R level, these operations will only be executed when you explicitly collect() the table.
See Also
Other Spark data frames: sdf_copy_to(), sdf_distinct(), sdf_random_split(), sdf_register(), sdf_sample(), sdf_sort()