com.salesforce.op.stages.impl.preparators.CorrelationType
Compute with Spearman's rank-order correlation
https://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient
The spark name of the correlation coefficient
Compute with Spearman's rank-order correlation
https://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient