[Tex/LaTex] How to position an element relative to an anchor

tikz-nodetikz-pgf

My code is:

\begin{center}
    \vspace{-20pt}
    \begin{tikzpicture}[mybox/.style={rectangle, draw, minimum width=10mm, minimum height=10mm}]
    \foreach \addr/\val [count=\x] in {$0$,$1$/$28$,$6$/$\infty$,$6$/$\infty$,$6$/$25$,$0$,$6$/$\infty$} {
        \node (node\x) [mybox] at (\x,0) {\addr};
        \node[above=5mm] at (\x,0) {\footnotesize \x};
        \node[below=5mm] at (\x,0) {\val};
    }
    \node at (node1.south west-100mm,0) [below=5mm] {Edge Weight:};
    \draw[ultra thick] (node1.south west) rectangle (node7.north east);
    \end{tikzpicture}
\end{center}

I get an error on the line \node (lab) at (node1.south west-100mm,0) [below=5mm] {Edge Weight:}; pertaining to the section (node1.south west-100mm,0) on using the anchor as a coordinate.

The error:

Package PGF Math Error: Unknown function 'node1' (in 'node1.south west-100mm'). \node at (node1.south west-100mm,0)

Package PGF Math Error: Unknown function 'node1' (in 'node1.south west-100mm'). …est-100mm,0) [below=5mm] {Edge Weight:};

I want the position of the node lab to be at a distance of (-100pt,0) from the south west anchor of node0. How do I do this?

I even tried writing:

(node1.south west)+(-1,0)

But that doens't work either. How do I solve this issue?

P.S. I know writing \path (node1.south west) node at +(-35pt,-8pt) {Edge Weight:}; would solve the problem, but is there a way to do this directly without using the path command and simply using the node command?

Best Answer

You can use xshift:

\documentclass{article}
\usepackage{tikz}
\begin{document}

    \begin{tikzpicture}[mybox/.style={rectangle, draw, minimum width=10mm, minimum height=10mm}]
    \foreach \addr/\val [count=\x] in {$0$,$1$/$28$,$6$/$\infty$,$6$/$\infty$,$6$/$25$,$0$,$6$/$\infty$} {
        \node (node\x) [mybox] at (\x,0) {\addr};
        \node[above=5mm] at (\x,0) {\footnotesize \x};
        \node[below=5mm] at (\x,0) {\val};
    }
    \node at ([xshift=-10]node1.south west) [below=5mm] {Edge Weight:};
    \draw[ultra thick] (node1.south west) rectangle (node7.north east);
    \end{tikzpicture}

\end{document}

With this small tweak your code produces:

enter image description here

For what it's worth, to make the code easier to read I would replace the for-loop with

    \foreach \addr/\val [count=\x] in {0,1/28,6/\infty,6/\infty,6/25,0,6/\infty} {
        \node (node\x) [mybox] at (\x,0) {$\addr$};
        \node[above=5mm] at (\x,0) {\footnotesize \x};
        \node[below=5mm] at (\x,0) {$\val$};
    }
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