Calculate coordinates using components of other coordinates

Question

I am trying to calculate a new coordinate in relation to two other cordinates. How can I use the x component of one coordinate and the y component of the other? Thanks in advance.

Minimal example:

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
  \begin{tikzpicture}
    \node at (0,0) (a){a};
    \node at (1,1) (b){b};
    \node at ($ (*xcomponent of a*-1,*ycomponent of b*+1) $)
  \end{tikzpicture} 
\end{document}

i hoped there was a something like /getxy(variable){x component} {y component} but if there is no such command think i will use \path(a) and\pgfgetlastxy{\Xa}{\Ya} — moku89, Jul 28 '16 at 08:08

score 1 · Answer 1 · edited Jun 10 '20 at 12:32

You can extract the coordinates via Extract x, y coordinate of an arbitrary point in TikZ and then perform the coordainte calculations:

Notes:

You should avoid the minimal class as per Why should the minimal class be avoided?

Code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
% https://tex.stackexchange.com/questions/33703/extract-x-y-coordinate-of-an-arbitrary-point-in-tikz
\newdimen\XCoord
\newdimen\YCoord
\newcommand{\ExtractCoordinateX}[2]{\path (#2); \pgfgetlastxy{\XCoord}{\YCoord}; \xdef#1{\XCoord}}%
\newcommand{\ExtractCoordinateY}[2]{\path (#2); \pgfgetlastxy{\XCoord}{\YCoord}; \xdef#1{\YCoord}}%
\begin{document}
  \begin{tikzpicture}
    \node at (0,0) (a){a};
    \node at (1,1) (b){b};
\ExtractCoordinateX{\NewX}{a}
\ExtractCoordinateY{\NewY}{b}
\coordinate (X) at (\NewX,\NewY);

\node [draw=red, shape=circle] at ($ (X)+ (-1,1) $) {X};

\end{tikzpicture} 
\end{document}

score 1 · Accepted Answer · answered Jul 28 '16 at 07:04

1

You may use the |- operation:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
  \begin{tikzpicture}
    \node at (0,0) (a){a};
    \node at (1,1) (b){b};
    \node at ($(a |- b) + (-1,1) $) {c};
  \end{tikzpicture} 
\end{document}

Or you may use the let operation (same result):

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
  \begin{tikzpicture}
    \node at (0,0) (a){a};
    \node at (1,1) (b){b};
    \path let \p1=(a), \p2=(b) in
    node at (\x1 - 1cm, \y2 + 1cm) {c};
  \end{tikzpicture} 
\end{document}

answered Jul 28 '16 at 07:04

Paul Gaborit

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In my dokument I tried |- and it worked after changenging a|-b to b|-a but I do not know how and why it works. – moku89 Jul 28 '16 at 07:56
@moku89 With b|-a, you get the x coordinate of b and the y coordinate of a: you get a coordinate vertically (|) aligned with b and horizontally (-) aligned with a. – Paul Gaborit Jul 28 '16 at 08:40

Calculate coordinates using components of other coordinates

2 Answers2

Notes:

Code: