# Package PGF Math Error: Unknown operator o' or of'

I am getting a weird error while trying to place a node above another node using the below= syntax.

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\node[] (node1) at (0, 0) {Node 1};
\node[
below = 5pt of node1
] (node2) {Node 2};
\end{tikzpicture}
\end{document}


The error message is:

Package PGF Math Error: Unknown operator 'o' or 'of' (in '5pt of node1').


How can I place nodes in relation to other nodes without getting an error message?

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Did you figure this out seconds after posting or did you already know and are posting it as an aid to others? –  Loop Space Jan 18 '13 at 14:40
Most definitely as a reference/help to others: blog.stackoverflow.com/2011/07/… I did not find a similar question on tex.sx. –  Felix Jan 18 '13 at 14:41
Ask-and-answer is most definitely fine (please see meta.tex.stackexchange.com/q/2943/86 for some site-specific comments on this), but do you think you could polish the question a little? In particular, could you post a MWE which produces the error. –  Loop Space Jan 18 '13 at 14:45
Thanks for the suggestion, I've edited and added a MWE. Feel free to edit as well. –  Felix Jan 18 '13 at 14:57

The <placement>=<distance> of <node>.<anchor> syntax only works with the advanced positioning library. The parts

• distance and
• of <node>.<anchor> are both optional as
• .<anchor> is too.

Depending of <placement> the anchor key of the to-be-placed node is internally set according to the following table. The third column shows the default <anchor> if the .<anchor> part is omitted. (The sans-positioning <placement> key is just a better-to-comprehend version of the anchor key.)

 <placement>    anchor        .<anchor>
——————————————————————————————————————————
above          north         .south
left           east          .west
below          north         .south
right          west          .east
––––––––––––––––––––––––––––––––––––––––––
base left      base east     .base west
base right     base west     .base east
mid left       mid east      .mid west
mid right      mid west      .mid east
––––––––––––––––––––––––––––––––––––––––––
above left     south west    .north east
above right    south east    .north west
below left     north west    .south east
below right    north east    .south west


If no <distance> is given, the value of node distance is taken.

Note that for the four bottom ones the <distance> part can consist of <vertical distance> and <horizontal distance>. (The same is true for the node distance key that is enhanced by the positioning library also.)

The on grid option sets both anchors (the one of the to-be-placed node as well as the referenced .<anchor>) to .center so that the nodes are placed in a grid.

The topics covered by the last two paragraphs are further explained in the PGF manual in section 16.5.3 “Advanced Placement Options”, pp. 185ff.

## Example (with positioning library)

### Code

\documentclass[tikz,border=2pt]{standalone}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[nodes=draw]
\node (node1) at (0, 0) {Node 1};
\node[below=5pt of node1] (node2) {Node 2};
\end{tikzpicture}
\end{document}


## Example (without positioning library)

Without the positioning library this can be achieved by combining

• the old <placement>=<distance> and
• the at=<node>.<opposite anchor> key,

where <opposite anchor> is the corresponding .<anchor> of the table above.

The correct anchor part is set without the positioning library, too.

### Code

\documentclass[tikz,border=2pt]{standalone}
\begin{document}
\begin{tikzpicture}[nodes=draw]
\node (node1) at (0, 0) {Node 1};
\node[below=5pt,at=(node1.south)] (node2) {Node 2};
\end{tikzpicture}
\end{document}


## Output

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Very thorough explanation, thanks! –  Felix Jan 18 '13 at 15:35
–  Qrrbrbirlbel Jan 19 '13 at 13:09

The positioning library is missing:

\usetikzlibrary{positioning}

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