[Tex/LaTex] What’s the difference between \path and \draw in Tikz

pgf-coretikz-pgf

The question is in the title: What is the difference between the commands \path and \draw in Tikz? The PGF and TikZ manual by Till Tantau tells me (on page 26 of the current version) that “\draw is just a shorthand for \path[draw]”.

In some of the answers I got to previous questions on how to draw certain figures using Tikz, some users have used a mixture of \path and\draw in their code, while others only seemed to use \draw.

The very helpful slides Marc van Dongen has on his website explaining the basic features of Tikz also contain a mixture of both, whilst mostly relying on the \draw command.

To remedy this confusion, I have as of now switched to using exclusivley \draw, but I find it very confusing.

What is the difference between the two commands? Should I be using both? When is it better to use \path instead of \draw and vice versa? When is it all the same? Are there things \path can do that \draw cannot?

Best Answer

Sometimes we only need a virtual path, or a totally transparent path just to compute some coordinates, intersections, and so on.

To do an invisible path we use \path and if you want to put some ink on it you use \draw.

Example: Here is an example where I used some paths to compute the intersections.

\documentclass{report}
\usepackage{amsthm,amsmath,amssymb}
\usepackage{tikz}
\usetikzlibrary{intersections}

\begin{document}
\begin{tikzpicture}[scale=2]\footnotesize 
\clip (-1.2,-.3) rectangle (4,1.75);
\begin{scope}[rotate=70]
\coordinate (q) at (0,0);
%
\draw[dashed] (q) circle (1);
\draw[dotted](0,-.8)--(0,.8)node[left=1.5em]{$\mathcal{K}$};
%
\path[name path=ray1] (q)-- (35:3cm);
\path[name path=ray2] (q)-- (0:3cm);
\path[name path=ray3] (q)-- (-40:3cm);
\path[name path=ray4] (q)-- (-60:3.5cm);
\path[name path=ray5] (q)-- (-70:4cm);
\draw[name path=circulo] (q)+(.4,0) circle (.4);
\draw[name path=vertical] (1.25,-4)node[above left=10pt]{$L$} -- (1.25,2);
%
\draw[name intersections={of=ray1 and vertical,by={b}}]  (q)--(b);
\draw[name intersections={of=ray2 and vertical,by={a}}]  (q)--(a);
\draw[dotted,name intersections={of=ray3 and vertical,by={v3}}]  (q)--(v3);
\draw[dotted,name intersections={of=ray4 and vertical,by={v4}}]  (q)--(v4);
\draw[dotted,name intersections={of=ray5 and vertical,by={v5}}]  (q)--(v5);
%
\path[name intersections={of=ray1 and circulo,by={btilde}}] ;
\path[name intersections={of=ray2 and circulo,by={atilde}}] ;
\path[name intersections={of=ray3 and circulo,by={c31,c32}}] ;
\path[name intersections={of=ray4 and circulo,by={c41,c42}}] ;
\path[name intersections={of=ray5 and circulo,by={c51,c52}}] ;
%
\draw (atilde)--(btilde);
\draw[rotate=35] (btilde) rectangle +(-.07,-.07);
\draw[rotate=0] (a) rectangle +(-.07,.07);
\foreach \p in {q,btilde,atilde,c32,c42,c52,b,a,v3,v4,v5}{
\draw[fill=white] (\p) circle (.7pt); }
%
\node[left=2pt] at (btilde){$\tilde b$};
\node[right=2pt] at (atilde){$\tilde a$};
\node[above=2pt] at (a){$a$};
\node[above=2pt] at (b){$b$};
\node[below=2pt] at (q){$q$};
\end{scope}
\end{tikzpicture}
\end{document}

enter image description here

Related Solutions

[Tex/LaTex] TikZ: difference between \node and \coordinate

Well, perhaps it's interesting to look at the pgfmanual :

\coordinate is a shortcut for \path ... coordinate[⟨options⟩](⟨name⟩)at(⟨coordinate⟩) ...;
and it's the same that node[shape=coordinate][]⟨options ⟩](⟨name ⟩)at(⟨coordinate ⟩){}, where the at part might be missing.

Since nodes are often the only path operation on paths, there are two special commands for creating paths containing only a node: \node Inside {tikzpicture} this is an abbreviation for \path node. \coordinate Inside {tikzpicture} this is an abbreviation for \path coordinate.
pgf and TikZ define three shapes, by default:
- rectangle,
- circle, and
- coordinate.
The coordinate shape is handled in a special way by TikZ. When a node x whose shape is coordinate is used as a coordinate (x), this has the same effect as if you had said (x.center). None of the special “line shortening rules” apply in this case. This can be useful ...
finally

The exact behaviour of shapes differs, shapes defined for more special purposes (like a, say, transistor shape) will have even more custom behaviors. However, there are some options that apply to most shapes.

It's why some default values like inner sep are different.

[Tex/LaTex] What’s the difference between TikZ anchors and coordinates

If you look at Jake's code, it has an optional argument, which by default is center, used in \pgfpointanchor. A quote from the manual:

\pgfpointanchor{ node }{ anchor }
This command is another “point command” like the commands described in Section 97. It returns the coordinate of the given anchor in the given node.

So you should really use those macros as

\node[above right] at (A.north east) {(\xcoord[north east]{A}, ycoord[north east]{A})};

As you've used them, \pgfpointanchor looks for a node called A.north east but the name of the node is A.

The reason this works with a coordinate is that a coordinate is really a node.

\documentclass[tikz, margin=5pt]{standalone}

\makeatletter
\newcommand\xcoord[2][center]{{%
    \pgfpointanchor{#2}{#1}%
    \pgfmathparse{\pgf@x/\pgf@xx}%
    \pgfmathprintnumber{\pgfmathresult}%
}}
\newcommand\ycoord[2][center]{{%
    \pgfpointanchor{#2}{#1}%
    \pgfmathparse{\pgf@y/\pgf@yy}%
    \pgfmathprintnumber{\pgfmathresult}%
}}
\makeatother

\pgfkeys{/pgf/number format/.cd,fixed,fixed zerofill,precision=2}

\begin{document}
\begin{tikzpicture}
\node[draw, minimum size=2cm] (A) {A};
\node[above right] at (A.north east) {(\xcoord[north east]{A},\ycoord[north east]{A})};
\end{tikzpicture}
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] TikZ: difference between \node and \coordinate

[Tex/LaTex] What’s the difference between TikZ anchors and coordinates

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