# Generating graphs with smooth edges?

Is there some way to produce these figures using TeX itself preferably using TikZ? If yes, then I would also like to add labels right next to the nodes rather than using a legend.

This is a screenshot from a paper I am reading and I would prefer using TeX to create them than using some external tools.

EDIT

I read the answer here but I would like to add the 'crosses' on the line instead of a gray colored line pointing to where the cross must exist. Moreover, I don't know how to change the crosses to the different symbols given in the diagram drawn above.

You can use to with the angles as parameter, at which the lines enter and leave nodes.

\draw (from-node) to[out=angle at from-node,in=angle at to-node] (to-node);


The angles are measured from the positive x-axis.

\documentclass[border=1mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes}
\begin{document}
\tikzset
{dest/.style={circle,draw,minimum width=1mm,inner sep=0mm},
start/.style={diamond,fill,draw,minimum width=1mm, minimum height=1mm,inner sep=0mm},
terminal/.style={circle,draw,minimum width=1.5mm,inner sep=0mm,label={[label distance=-2.75mm]{\tiny+}}}
}
\begin{tikzpicture}
\node[start,label={[right]:$s$}] (s) at (0,0) {};
\node[dest,label={[left]:$d_1$}] (d1) at (-1,0.5) {};
\node[dest,label={[right]:$d_2$}] (d2) at (0.3,0.6) {};
\node[dest,label={[right]:$d_3$}] (d3) at (0,1.5) {};
\node[dest,label=$d_4$] (d4) at (-1,2) {};
\node[terminal,label={[left]:$t$}] (t) at (-0.9,1.3) {};
\draw (s) to[out=170,in=-90] (d1);
\draw (d1) to[out=70,in=-100] (d2);
\draw (d2) to[out=100,in=-60] (d3);
\draw (d3) to[out=120,in=30] (d4);
\draw (d4) to[out=-110,in=100] (t);
\end{tikzpicture}
\end{document}

• Oh yes that's it! Thanks for tolerating my OCD! :P – Banach Tarski Nov 27 '16 at 14:12
• @BanachTarski First, I feel deeply honoured to be addressed by Tarski ;) Second, I've added node labels. – gernot Nov 27 '16 at 14:19
• @gernot I bet you didn't know that his first name was Banach, though, eh? ;-) – wchargin Nov 28 '16 at 2:49

To get a more automated smooth connection with less of the manual labour you can use \draw [smooth] plot coordinates {(0,0) (1,0) (1,0) (1,1)}; where the key tension=1.5 specifies the tightness to the straight line. See this answer for some more details discussion of the functionality of this sort of command.

Using expl3 (I loaded xparse and used \NewDocumentCommand rather than \newcommand but that bit could be done with LaTeX2e) I've defined a new command which takes a set of coordinates separated by ; (this could be any reasonable separator, I used ; over , as coordinates naturally have the (a,b) description) as a single input. The coordinates are then split up into a seq variable (\l__banachtarski_coords_seq) from which they are extracted for plotting. As well as an optional argument which sets a value for tension of the plot.

To my knowledge TikZ does not offer mark first, mark last, and mark middle type commands in \draw plot options so I first plot a smooth line between all the points with \draw plot [smooth, tension=1.5] coordinates { \seq_use:Nn \l__banachtarski_coords_seq { ~ } }; which produces the smooth line and then to place the marks I use a rather inefficient approach which places a mark at the first coordinate and a mark at the second using distinct marks, removing them from \l__banachtarski_coords_seq in the process

\seq_pop_left:NN \l__banachtarski_coords_seq \l__banachtarski_temp_tl
\draw plot [only~marks,mark=diamond*,mark~options={fill=black}] coordinates {
\l__banachtarski_temp_tl
};

\seq_pop_right:NN \l__banachtarski_coords_seq \l__banachtarski_temp_tl
\draw plot [only~marks,mark=oplus*,mark~options={fill=gray}] coordinates {
\l__banachtarski_temp_tl
};


and then plotting the remaining middle coordinates with a third mark

\draw plot [only~marks,mark=*,mark~options={fill=gray}] coordinates {
\seq_use:Nn \l__banachtarski_coords_seq { ~ }
};


only~marks (which draws the marks but no connecting lines) has to be used rather than only marks as this is all happening inside \ExplSyntaxOn ... \ExplSyntaxOff although it is probably only needed for plotting the final set of marks.

Thus (using the same coordinates as gernot's answer which offers much finer control at more expense of effort)) one can generate from

\documentclass{article}
\usepackage{xparse}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\ExplSyntaxOn
\seq_new:N \l__banachtarski_coords_seq
\tl_new:N \l__banachtarski_temp_tl

\NewDocumentCommand \smoothgraph { O{1} m }
{
\seq_set_split:Nnn \l__banachtarski_coords_seq { ; } { #2 }

\draw plot [smooth, tension=#1] coordinates { \seq_use:Nn \l__banachtarski_coords_seq { ~ } };

\seq_pop_left:NN \l__banachtarski_coords_seq \l__banachtarski_temp_tl
\draw plot [only~marks,mark=diamond*,mark~options={fill=black}] coordinates { \l__banachtarski_temp_tl };

\seq_pop_right:NN \l__banachtarski_coords_seq \l__banachtarski_temp_tl
\draw plot [only~marks,mark=oplus*,mark~options={fill=gray}] coordinates { \l__banachtarski_temp_tl };

\draw plot [only~marks,mark=*,mark~options={fill=gray}] coordinates { \seq_use:Nn \l__banachtarski_coords_seq { ~ } };
}

\ExplSyntaxOff

\begin{document}
\begin{tikzpicture}
\smoothgraph{(0,0);(-1,0.5);(0.3,0.6);(0,1.5);(-1,2);(-0.9,1.3)}
\end{tikzpicture}
\begin{tikzpicture}
\smoothgraph[2]{(0,0);(-1,0.5);(0.3,0.6);(0,1.5);(-1,2);(-0.9,1.3)}
\end{tikzpicture}
\end{document}