"Network Propaganda": A Small Thing that Bothered me

I admit it is a small thing, but one particular thing in Network Propaganda eats away at me -- the three dimensional graph above.  News coverage of immigration apparently deviated from the usual rule that the center-left, center, and left media formed one cluster and the rightwing media formed another, with almost not center-right.  In this case, there were enough differences that one axis was not enough -- the authors felt the need for three.  Unfortunately, they neglected to label the axes, so I am not sure what they mean.

The authors did note that the difference between rightwing and mainstream media on immigration was not just how friendly or hostile they were.  Rather, rightwing media tended to equate all immigration with Islam and terrorism, while mainstream media (accurately) portrayed most immigration as coming from Latin America. Leftwing media also focused on the war in Syria and refugees, actually giving more emphasis to Muslims that center and center-left, but seeing Muslims as victims, rather than terrorists. Presumably that is the X-axis -- the degree to which outlets discussed Muslims.

White nationalist and neo-Nazi websites were more openly racist than any mainstream sites, including mainstream rightwing sites, and rife with anti-Semitic conspiracy theories not seen anywhere else.  The biggest words in their word clouds were "Jew" and Jewish," words not seen in any other word clouds.  Presumably the y-axis is antisemitism, a subject seen in white nationalist and neo-Nazi articles but not anywhere else.

The authors also make clear that the center-right has a different pattern, not seen anywhere else, as evidenced by the National Review, Reason, and Red State, which are all positioned apart along the z-axis.  Unfortunately, the book never says what made the center-right different, or what the z-axis is.  It is frustrating.