x
Object of class data frame containing columns 'sample', reference',
'variant' for 'MGI' file or 'Tumor_Sample_Barcode', 'Reference_Allele',
'Tumor_Seq_Allele1', 'Tumor_Seq_Allele2' for 'MAF' file
z
Object of class data frame containing columns "sample", "variable",
"value" denoting clinical information