# How to partially make a segment of a path dashed?

I have two stocks, A and B. These two "meet" each other at rates q(x), and f(x), by going through a joint-state process called X. Then, A becomes a, and B becomes b.

I thought about visualizing the flowchart as in the attached box. However, I'm clueless as to how solve this within tikz. It'd be best if the arrows are dashed arrows while "inside of X". With protest, here's as far as I came.

\documentclass[border=1in]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}

\tikzstyle{block} = [rectangle, draw, fill=blue!20,
text width=5em, text centered, rounded corners, minimum height=4em]

\begin{document}
\begin{tikzpicture}
\node [block] (X) {X};
\node [block] [below left=of X] (A) {A};
\node [block] [above left=of X] (a) {a};
\node [block] [below right=of X] (B) {B};
\node [block] [above right=of X] (b) {b};

\path[->] (A) edge[bend right=90] node [left] {} (a);
\path[->] (B) edge[bend left=90] node [left] {} (b);

\end{tikzpicture}
\end{document}

• The point is "adding what you've tried so far". – vaettchen Dec 22 '18 at 7:17

Just divide the path in three if you want the second part dashed.

If you write NodeName.degreee (for example X.130) you can position the end or the beginning of the path exactly where you need. Imagine the node is a circle angle with the east anchor = 0 degrees, so the south anchor is -90, the north = 90, the east = 180, etc.

\documentclass[border=1in]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}
\tikzset{
block/.style={
rectangle, draw, fill=blue!20,
text width=5em, text centered, rounded corners, minimum height=4em
}
}

\begin{document}
\begin{tikzpicture}
\node [block] (X) {X};
\node [block] [below left=of X] (A) {A};
\node [block] [above left=of X] (a) {a};
\node [block] [below right=of X] (B) {B};
\node [block] [above right=of X] (b) {b};

\draw (A) to[bend right] (X.-130) node[below left=4pt and 5pt] {$q(x)$};
\draw[dashed] (X.-130) to[bend right, looseness=.2] (X.130);
\draw[->] (X.130) to[bend right] (a);

\draw (B) to[bend left] (X.-50) node[below right=4pt and 5pt] {$f(x)$};
\draw[dashed] (X.-50) to[bend left, looseness=.2] (X.50);
\draw[->] (X.50) to[bend left] (b);

\end{tikzpicture}
\end{document} Edit: gorgeous marmot's answer could be simplified without using reverse clipping and putting the straight line behind the X node, like in marya's answer but using on background layer from backgrounds library to not draw it twice.

\documentclass[border=1in]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning,backgrounds}
\tikzset{
block/.style={
rectangle,
text width=5em,  text centered, rounded corners, minimum height=4em, draw, fill=blue!20
},
}

\begin{document}
\begin{tikzpicture}
\node[block] (X) {X};
\node [block] [below left=of X] (A) {A};
\node [block] [above left=of X] (a) {a};
\node [block] [below right=of X] (B) {B};
\node [block] [above right=of X] (b) {b};

\begin{scope}[on background layer]
\path[->] (A) edge[bend right=90] node[near start, above left] {$q(x)$} (a);
\path[->] (B) edge[bend left=90]  node[near start, above right] {$f(x)$} (b);
\end{scope}

\begin{scope}[dashed]
\clip[rounded corners] (X.north west) rectangle (X.south east);
\path[->] (A) edge[bend right=90] (a);
\path[->] (B) edge[bend left=90]  (b);
\end{scope}
\end{tikzpicture}
\end{document} • Oh, now after seeing the image, I understand I wasn't being clear enough. Ive updated the picture to emphasize what I mean by "dashed while inside of X"... sorry about that – FooBar Dec 22 '18 at 8:03
• @FooBar See my renewed answer – CarLaTeX Dec 22 '18 at 8:11

Here is a proposal using reverseclip and use path to draw the dashed path inside and the solid one outside. Please note that \tikzstyle is slightly deprecated.

\documentclass[border=1in]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}
\makeatletter % https://tex.stackexchange.com/a/38995/121799
\tikzset{
use path/.code={\pgfsyssoftpath@setcurrentpath{#1}}
}
\makeatother
\tikzset{remember path/.style={save path=\tmprotect}}
% https://tex.stackexchange.com/a/12033/121799
\tikzset{reverseclip/.style={insert path={(current bounding box.north
east) rectangle (current bounding box.south west)}}}

\tikzset{block/.style={rectangle, draw, fill=blue!20,
text width=5em, text centered, rounded corners, minimum height=4em}}

\begin{document}
\begin{tikzpicture}
\node [block,save path=\pathX] (X) {X};
\node [block] [below left=of X] (A) {A};
\node [block] [above left=of X] (a) {a};
\node [block] [below right=of X] (B) {B};
\node [block] [above right=of X] (b) {b};

\begin{scope}
\clip[use path=\pathX,reverseclip];
\path[->] (A) edge[bend right=90] (a);
\path[->] (B) edge[bend left=90]  (b);
\end{scope}
\begin{scope}[dashed]
\clip[use path=\pathX];
\path[->] (A) edge[bend right=90] (a);
\path[->] (B) edge[bend left=90]  (b);
\end{scope}

\end{tikzpicture}
\end{document} • @CarLaTeX I would not say it is strictly "better" but each of them has its own advantage. (I upvoted your post, too, of course.) – user121799 Dec 22 '18 at 9:31
• @CarLaTeX Thanks for saying that but I guess it is a matter of taste.So we cannot argue about it, ;-) – user121799 Dec 22 '18 at 9:35
• @CarLaTeX To be honest, I like mine better because if the path in yours would hit a rounded corner, it would get clipped incorrectly. This is why I am doing the use path trick. (And personally I do not find reverseclip inelegant, but that's a matter of taste.) – user121799 Dec 22 '18 at 14:47
• @CarLaTeX I would nevertheless like to argue that you could add [rounded corners] to \clip such that it becomes \clip[rounded corners] (X.north west) rectangle (X.south east); (which has another simplification: rectangle and 2 corners instead of 4 corners and cycle). To see where that may matter, add a path \draw (A.50) -- (b.-130);. Notice also that use path is not something exotic. save path is already part of plain vanilla TikZ, and use path is part of some common libraries like spath3 (and really useful IMHO). – user121799 Dec 22 '18 at 15:34
• @CarLaTeX I guess it is really a matter of taste. After all we we are all TikZ beginners. ;-) (Instead of using a phantom node, you could just draw the solid paths on the background, which would avoid to draw the node twice.) – user121799 Dec 22 '18 at 17:01

Well, the easiest solution I came up is this one

\documentclass[border=1in]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}

\tikzstyle{block} = [rectangle, draw, fill=blue!20,
text width=5em, text centered, rounded corners, minimum height=4em]

\begin{document}
\begin{tikzpicture}
\node [block] (X) {X};
\node [block] [below left=of X] (A) {A};
\node [block] [above left=of X] (a) {a};
\node [block] [below right=of X] (B) {B};
\node [block] [above right=of X] (b) {b};

\path[->] (A) edge[bend right=90] node [left,pos=0.3] {$q(r)$} (a);
\path[->] (B) edge[bend left=90] node [right,pos=0.3] {$f(r)$} (b);
\node [block] (X) {X};
\path[->,dashed] (A) edge[bend right=90] node [left,pos=0.3] { } (a);
\path[->,dashed] (B) edge[bend left=90] node [right,pos=0.3] { } (b);
\end{tikzpicture}
\end{document} 