def add_assay(self, name, assay):
if not type(assay) is numpy.ndarray:<EOL><INDENT>raise Exception("<STR_LIT>")<EOL><DEDENT>elif not assay.shape == (self.compound_count,):<EOL><INDENT>raise Exception("<STR_LIT>"<EOL>"<STR_LIT>")<EOL><DEDENT>elif name in self.raw_assays.keys():<EOL><INDENT>raise Exception("<STR_LIT>"<EOL>"<STR_LIT>")<EOL><DEDENT>self.raw_assays[name] = assay<EOL>self.converted_assays[name] = assay<EOL>
Add an assay to the material.

:param name:  Assay name.
:param assay: Numpy array containing the compound mass fractions for
  the assay. The sequence of the assay's elements must correspond to
  the sequence of the material's compounds.