% Minimal plain-TeX example using the format-specific wrapper.
\input p-luacoolprop.tex
\pgfplotsset{compat=1.18}
\LCPPVDiagram[
  fluid=R134a,
  specific volume axis unit=lkg,
  isotherm=true,
  isentrope=true,
  quality step=0.2,
  temperature values={-20,0,20,40,60,80},
  entropy values={1.6,1.8,2.0},
  labels=true
]
\bye

.