cor_prep: Prepare correlation data for plotting
In cRegulome: Obtain and Visualize Regulome-Gene Expression Correlations in Cancer

Not meant to be called directly by the user.

1	cor_prep(ob, study, add_dir = TRUE, add_corr = TRUE)

`ob`	A cmicroRNA or cTF object such as this returned by calling cmicroRNA or cTF.
`study`	A `character` vector of The Cancer Genome Atlas (TCGA) study identifiers. To view the available studies in TCGA project, https://tcga-data.nci.nih.gov/docs/publications/tcga. When left to default `NULL` all available studies will be included.
`add_dir`	A `logical` default TRUE for whether to add a column called Direction that has the direction of the correlation; positive or negative.
`add_corr`	A `logical` default TRUE for whether to add a column called Correlation that has the absolute value of the correlation