Add m4 macro processor as a MADlib requirement.
SQL-based algorithms for machine learning, data mining and statistics that run at scale
within a database engine, with no need for transferring data between Greenplum Database and
other tools. </p>
+ <p>MADlib requires the <codeph>m4</codeph> macro processor version 1.4.13 or later.</p>
<p>MADlib can be used with PivotalR, an R package that enables users to interact with data
resident in Greenplum Database using the R client. See <xref href="#topic_dxp_vq2_sv"
format="dita"/>.</p>
