Hi,
Thanks Herbert and Hans, your solutions work both
Fabrice

2016-08-16 20:35 GMT+02:00 Herbert Voss <Herbert.Voss@fu-berlin.de>:
Am 16.08.2016 um 16:52 schrieb Fabrice Couvreur:

\usemodule[pgfplots]

\pgfplotsset{compat=1.13}
\usetikzlibrary[intersections]
\usepgfplotslibrary[fillbetween]

\starttext

\starttikzpicture[/pgf/declare
function={f(\x)=(1/8)*(\x^3-2.5*\x^2-3*\x+4.5);},]
\switchtobodyfont[8pt]
\startaxis

[...]
\starttext

\starttikzpicture[
  /pgf/declare function={f(\x)=(1/8)*(\x^3-2.5*\x^2-3*\x+4.5);},
  font={\switchtobodyfont[8pt]}
]
%
\startaxis
[...]

Herbert

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