The help is correct for muparser1, muparser2 changed 'if' function syntax.
see bottom of the page https://beltoforion.de/article.php?a=muparser&p=features
File: libscidavis/src/MyParser.cpp line 152.
blabla="if(e1, e2, e3): if e1 then e2 else e3.";
should be:
blabla="(e1) ? (e2) : (e3): if e1 then e2 else e3."
or something similar.
Scilab version: 2.1.4
Arch linux
Fixed here