TikZ: How to rotate and then shift?

Question

I'm trying to rotate a node and then shift it along the X axis. If I do [rotate=90, xshift=-20pt], the node will first shift and then rotate.

Answer 1

You could nest the rotated object inside a shifted scope, i.e.

\begin{scope}[xshift=-20pt]
    \draw [rotate=90] ...;
\end{scope}

Answer 2

The scope is not necessary. You have two solutions

1) with cm={0,1,-1,0,(-20pt,0cm)}

2) you can try to change the order of your transformations with xshift=-20 pt,rotate=90and not rotate=90,xshift=-20 pt.

\documentclass{scrartcl}
\usepackage{tikz} 

\begin{document}

\begin{tikzpicture}   
 \draw[red,->] (0,0) -- (1,1);   
 \draw[blue,->,cm={0,1,-1,0,(-20pt,0cm)}] (0,0) -- (1,1);
\end{tikzpicture}

\begin{tikzpicture}
 \draw[red,->] (0,0) -- (1,1);   
 \draw[blue,->,xshift=-20 pt,rotate=90]  (0,0) -- (1,1);
 \draw[green,->,rotate=90,xshift=-20 pt] (0,0) -- (1,1);
\end{tikzpicture}

\end{document}