/// <summary>
/// Returns a new DataFrame by sampling a fraction of rows.
/// </summary>
/// <param name="withReplacement"> Sample with replacement or not. </param>
/// <param name="fraction"> Fraction of rows to generate. </param>
/// <param name="seed"> Seed for sampling. If it is not present, a randome long value will be assigned. </param>
// Python API: https://github.com/apache/spark/blob/branch-1.4/python/pyspark/sql/dataframe.py
// sample(self, withReplacement, fraction, seed=None)
public DataFrame Sample(bool withReplacement, double fraction, long?seed)
{
long v;
if (seed.HasValue)
{
v = seed.Value;
}
else
{
v = ((long)random.Next()) << 32 + random.Next();
}
return(new DataFrame(dataFrameProxy.Sample(withReplacement, fraction, v), sparkContext));
}