Centering caption in figure environment with a tikzpicture

Question

I'm trying to center a tikzpicture and a caption inside the figure environment, but when I compile something is off. It seems as if the caption and the tikzpicture are centering with respect to diferent referenes. I'm using Overleaf.

\begin{figure}[H]
\centering
\begin{tikzpicture}[scale=1.0]
\begin{axis}[ ymin=0, xlabel = variáveis aleatórias, ylabel = frequência]

\addplot [
    domain=0:10, 
    samples=100, 
    color=red]
    {exp(-x)};
\end{axis}
\end{tikzpicture}
\caption{Some figure}
\end{figure}

Answer 1

As Sigur points out, the caption is centered w.r.t. the full tikzpicture, not just the plot, but the plot with labels. If you really don't want this, you might mess around with the bounding box.

\documentclass{article}
\usepackage{float}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\usepackage{lipsum}
\begin{document}
\lipsum[1]
\begin{figure}[H]
\centering
\begin{tikzpicture}[scale=1.0]
\begin{pgfinterruptboundingbox}
\begin{axis}[ ymin=0, xlabel = variáveis aleatórias, ylabel = frequência]

\addplot [
    domain=0:10, 
    samples=100, 
    color=red]
    {exp(-x)};
\end{axis}
\end{pgfinterruptboundingbox}
\path[use as bounding box] ([yshift=-8mm]current axis.south west) rectangle (current axis.north east);
\end{tikzpicture}
\caption{Some figure}
\end{figure}
\lipsum[2]
\end{document}

Other options include shifting the caption to the left, or, what might be more elegant, to add the same space to the bounding box on the right.

\documentclass{article}
\usepackage{float}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\usetikzlibrary{calc}
\usepackage{lipsum}
\begin{document}
\lipsum[1]
\begin{figure}[H]
\centering
\begin{tikzpicture}[scale=1.0]
\begin{axis}[ ymin=0, xlabel = variáveis aleatórias, ylabel = frequência,ylabel style={alias=ylab}]

\addplot [
    domain=0:10, 
    samples=100, 
    color=red]
    {exp(-x)};
\end{axis}
\path let \p1=($(current axis.west)-(ylab.north)$) in (current axis.east) -- ++(\x1,0);
axis.north east);
\end{tikzpicture}
\caption{Some figure}
\end{figure}
\lipsum[2]
\end{document}

This saves you from having to add an yshift by hand.

Answer 2

Here is a variant of Marmot's solution using the calc tikzlibrary and the [name=...] option for axis.

\documentclass{article}
\usepackage{float}
\usepackage{pgfplots}
\usetikzlibrary{calc}
\pgfplotsset{compat=1.16}
\usepackage{lipsum}
\begin{document}
\lipsum[1]
\begin{figure}[H]
\centering
\begin{tikzpicture}[scale=1.0]
\begin{axis}[ymin=0, xlabel = variáveis aleatórias, ylabel = frequência,
    name=border]
\addplot [
    domain=0:10, 
    samples=100, 
    color=red]
    {exp(-x)};
\end{axis}
% center tikzpicture relative to axis (border)
\path ($(border.center)!-1!(current bounding box.west)$);
\draw[blue] (current bounding box.south west) rectangle (current bounding box.north east);% demo only
\end{tikzpicture}
\caption{Some figure}
\end{figure}
\lipsum[2]
\end{document}

---

This solution places the caption inside the tikzpicture, within the axis border (horizontally). This makes the tikzpicture smaller but provides much less space for the caption.

\documentclass{article}
\usepackage{float}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\usepackage{lipsum}

\newlength{\tempwidth}

\begin{document}
\lipsum[1]
\begin{figure}[H]
\centering
\begin{tikzpicture}[scale=1.0]
\begin{axis}[ymin=0, xlabel = variáveis aleatórias, ylabel = frequência,
    name=border]
\addplot [
    domain=0:10, 
    samples=100, 
    color=red]
    {exp(-x)};
\end{axis}
% center tikzpicture relative to axis (border)
\pgfextractx{\tempwidth}{\pgfpointdiff{\pgfpointanchor{border}{west}}{\pgfpointanchor{border}{east}}}%
\node[below] at (border.south |- current bounding box.south) {\begin{minipage}{\tempwidth}
    \caption{Some figure}
\end{minipage}};
\draw[blue] (current bounding box.south west) rectangle (current bounding box.north east);% demo only
\end{tikzpicture}

\end{figure}
\lipsum[2]
\end{document}