Given a sequence of $n$ non-negative numbers $x=(x_1,\dots,x_n)$,
where $x_i \ge x_j$ for $i \le j$,
the $l_p$-index for $p=\infty$ equals to
$$l_p(x)=\arg\max_{(i,x_i), i=1,\dots,n} { i x_i }$$
if $n \ge 1$, or $l_\infty(x)=0$ otherwise.
Note that if $(i,x_i)=l_\infty(x)$, then
$$MAXPROD(x) = i x_i,$$ where $MAXPROD$ is the index proposed in (Kosmulski, 2007).For the definition of the $l_p$-index for $p < \infty$ we refer
to (Gagolewski, Grzegorzewski, 2009a).
If disable.check is set to FALSE, then
eventual NA values are removed from the input vector.
If a non-increasingly sorted vector is given as input (set sorted.dec to TRUE)
the result is computed in linear time (see Gagolewski, Debski, Nowakiewicz, 2009b).