# Aligning nodes in different tikzpictures

It is possible to align the baseline of two nodes in different tikzpictures. I have a tikz in an align environment as in the following example code

\begin{align}
&\tikz[remember picture]{\node(I){};} \to \Delta r \leq \frac{r}{n-1}\\
&\to\Delta r - \frac{r}{n-2} \leq 0
\end{align}


and another tikz after this as the following one

\tikz[overlay,remember picture]{\node at(I){$\Delta r \to \frac{r}{n-1}$};}


How can I make the baseline of the two nodes aligned without messing up the alignment in the align environment?

Edit 1: Minimal (not) working example

\documentclass[]{beamer}
\usepackage[english]{babel}

\usepackage{tikz}

\begin{document}
\begin{frame}
\begin{align*}
&\tikz[remember picture]{\node(I){};} \to \Delta r \leq \frac{r}{n-1}\\
&\to\Delta r - \frac{r}{n-2} \leq 0
\end{align*}
\visible<2->{\tikz[overlay, remember picture]{\node[anchor=east] at(I.west){$\Delta r \to \frac{r}{n-1}$};}}
\end{frame}
\end{document}


In this example, the arrows are not aligned both vertically and horizontally.

The desired output:

The vertical alignment problem is because your TikZ node, although void, has a size different from zero. The second one can be solved by the base anchors.

Anyway, you should look at the tikzmark library.

\documentclass[]{beamer}
\usepackage[english]{babel}

\usepackage{tikz}

\begin{document}
\begin{frame}
\begin{align*}
&\tikz[remember picture]{\node[inner sep=0pt, outer sep=0pt](I){};} \to\Delta r \leq \frac{r}{n-1}\\
&\to\Delta r - \frac{r}{n-2} \leq 0
\end{align*}
\visible<2->{\tikz[overlay, remember picture]{\node[anchor=base east] at(I.base){$\Delta r \to \frac{r}{n-1}$};}}
\end{frame}
\end{document}


Still is not perfect though --- some extra space is added by tikz. Better using overlay:

\documentclass[]{beamer}
\usepackage[english]{babel}

\usepackage{tikz}

\begin{document}
\begin{frame}
\begin{align*}
&\tikz[remember picture, overlay]{\node(I){};}\to\Delta r \leq \frac{r}{n-1}\\
&\to\Delta r - \frac{r}{n-2} \leq 0
\end{align*}
\visible<2->{\tikz[overlay, remember picture]{\node[anchor=base east] at(I.base){$\Delta r \to \frac{r}{n-1}$};}}
\end{frame}
\end{document}


• I knew about the tikzmark library, but I was hoping for a handmade solution. @Rmano I was about to point out about the white space, but this works perfectly. Thank you. – Luca Benatti Mar 13 at 11:22