Pgfplots: How to change the axis multiplier symbol

I want to define manually the symbol that multiplies the x axis. How to do it so?

As example: Instead of the scientific notation $\cdot 10^2$, I would like to have $\cdot \Delta_x$.

Assuming you're actually talking about pgfplots (which is built on TikZ, but not the same as TikZ), you need xtick scale label code/.code={$\cdot \Delta_{x}$}.

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
domain=0:1e9,samples=2,
xtick scale label code/.code={$\cdot \Delta_{x}$}
]
\end{axis}
\end{tikzpicture}
\end{document}


Or you can turn off any such label, and place a node manually:

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
domain=0:1e9,samples=2,
xtick scale label code/.code={},
name=ax
]
\node [below left] at (ax.outer south east) {$\cdot \Delta_{x}$};

• Thank you ! But this seems to replace the $10^i$ value. What happens when this is not present (this is my case)? For instance, in the example you gave, by changing to ..., domain=0:1, samples=2, ...., then the $\Delta_x$ is not produced. – pancho Feb 20 '18 at 19:11