contexttikz-pgf
As I understand it, the basic unit length in TikZ is 1cm, so that for example
\draw (0,0) -- (1,0);
draws a line 1cm in length. What I want to do is to redefine that length so that all drawings in my document are a different size. Using ConTeXt, how can I do this?
It is simply due to a forgotten square root step. It can be solved by adding sqrt.
\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[scale=3]
\node[left] (O) at (0,0) {$O$};
%Draw the Circle around it all
\draw[semithick] (0,0) circle (1);
%Draw lines to the top
\foreach \x in {-4,...,4}
\draw[red,very thick] (\x/8,0) -- +(0,{sqrt(1-\x/8*\x/8)});
\end{tikzpicture}
\end{document}
As is explained in How do I draw shapes inside a tikz node? pics can be used for defining new objects. My main problem using pics is how to place where you want because they aren't nodes and positioning them is not so easy.
Following code shows how to define EDFA block.
EDFA/.pic={
\begin{scope}[scale=.5]
\draw (-1,0) coordinate (in) -- (-1,1) -- (1,0) coordinate (out) -- (-1,-1) -- cycle;
\node[anchor=north,inner sep=2pt] at (0,-1) {$1$};
\end{scope}
In this case, coordinate (-1,0) will act as west anchor and 1,0 as east. Both point will have an special name for further reference. Every pic is placed according its own origin (0,0). You can use Claudio's answer to Anchoring TiKZ pics for better positioning.
As your example was simple, I'd prefer to star with EDFA and place Source and Sink after it.
\documentclass[]{article}
% tikz
\usepackage{tikz}
\usetikzlibrary{positioning} %relative positioning
\begin{document}
\tikzset{%
EDFA/.pic={
\begin{scope}[scale=.5]
\draw (-1,0) coordinate (in) -- (-1,1) -- (1,0) coordinate (out) -- (-1,-1) -- cycle;
\node[anchor=north,inner sep=2pt] at (0,-1) {$1$};
\end{scope}
}
}
\begin{tikzpicture}[
block/.style={draw},
]
\draw pic (edfa) {EDFA};
\node[block, left=of edfain] (source) {Source};
\node[block, right= of edfaout] (sink) {Sink};
\draw[->] (source) -- (edfain);
\draw[->] (edfaout) -- (sink);
\end{tikzpicture}
\end{document}
I understand that your components are more complex than EDFA because for this particular case an isosceles triangle node with a label will do the work and it can be used as a node and not as a pic:
\documentclass[]{article}
% tikz
\usepackage{tikz}
\usetikzlibrary{positioning} %relative positioning
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}[
block/.style={draw},
edfa/.style={isosceles triangle, minimum width=1cm,
draw, anchor=west, isosceles triangle stretches,
minimum height=1cm, label=-80:#1}
]
\node[block] (source) {Source};
\node[edfa=1, right=of source] (edfa) {};
\node[block, right= of edfa] (sink) {Sink};
\draw[->] (source) -- (edfa);
\draw[->] (edfa) -- (sink);
\end{tikzpicture}
\end{document}
Best Answer
You can set the units length in TikZ for X, Y and even Z coordinates independently using the
x,yandzkeys:See the
pgfmanualp.249 section 22.2 The XY- and XYZ-Coordinate Systems.Note that TikZ actually doesn't have unit length, but uses vectors. The above keys therefore also accept
(a,b)coordinates (which must be enclosed in{ }to hide the,). The X and Y unit vectors do not need to be orthogonal to each other. The above code is the short version of[x={(2cm,0cm)},y={(0cm,1.5cm)}].You can also use the mentioned option
scaleas well, but I would prefer the above options. One difference will be that coordinates with explicit units are scaled as well withscale. For example(2cm,2)will be 3cm in both directions whenscale=1.5is set, but(2cm,3cm)withx=1.5cm,y=1.5cm.One problem with the use of vectors is that you can't access the effective unit length even for the default setup of an XY (no Z) orthogonal coordinate system. I personally needed that for my
tikz-timingpackage. You need to use PGF code for this:\pgfpointxy{1}{1}will give you the X and Y unit length as\pgf@xand\pgf@y. But note that these length registers will be overwritten by the next PGF or TikZ command.