[Tex/LaTex] Using Condition (If/Else) Inside Loop (For) In Tikz

conditionalsgridstikz-pgf

In my previous post, I have asked how to use two loops to construct a grid with values inside it. A wonderful answer was given by Andrew Swann .

\documentclass{article}

\usepackage{tikz}

\begin{document}

\def\n{6}
\def\m{8}
\def\s{1.5cm}
\tikz\draw grid[step=\s](\n*\s,\m*\s) foreach[evaluate] \x  in {1,...,\n}
  { foreach[evaluate={\z = int(min(\x,\n+1-\x)+\n*min(\y-1,\m-\y)/2)}] \y in {1,...,\m}
  {({\s*(.5+(\x-1))},{\s*(\m+.5-\y)}) node{$a=\z$}}};

\end{document}

he has provided a formula \z which can be modified for different arrangement of values.

For example, I did-

[evaluate= {\z = int(\x+\n*min(\y-1,\m+\y))}]

which gives-

1 2 3 4

5 6 7 8

9 10 11 12

for 3*4 grid. But if I want –

1 2 2 1

3 4 4 3

5 6 6 5

7 8 8 7

and ,

1 2 3 4

5 6 7 8

0 9 10 0

0 11 12 0

0 13 14 0

I could not do it! I am really having hard time to use loop and if else condition. Probably , I am too much used to C++ and similar things where I can easily do a=a+1 or write if condition. I can think of an way to print above value-arrangements, using Condition (if/else), but I don't know where to put it (I have tried, but all were wrong).

So,my question is, how to put Condition (if/else) before \z so that I can print output as I have shown above?

Best Answer

You could easily use ifthenelse in the tikz node:

\documentclass{minimal}
\usepackage{tikz}
\usepackage{ifthen}

\begin{document}

\def\n{4}
\def\m{4}
\def\s{1.5cm}
\tikz\draw grid[step=\s](\n*\s,\m*\s) 
  foreach[evaluate] \x  in {1,...,\n} { 
    foreach[evaluate={
      \zt = int(\x+\n*min(\y-1,\m+\y));
      \zb = int(\x+(\n-2)*min(\y-1,\m+\y)+3)
    }] \y in {1,...,\m} {
      ({\s*(.5+(\x-1))},{\s*(\m+.5-\y)}) node{$a=\ifthenelse{\y>2}{\ifthenelse{\x=1 \OR \x>3}{0}{\zb}}{\zt}$}
    }
  };

\end{document}

This should create the third grid you wanted.

Also see the answer to the following question for more examples with ifthenelse and loops: If-then-else inside TikZ graph?

Related Solutions

[Tex/LaTex] How to dynamically name and store macros/variables in \foreach in TikZ for later use

Here's a way to store your \label in relation with \x and \y via the two macros \storelabel and \getlabel.

\documentclass{article}
\usepackage{tikz}

\newcommand\storelabel[2]{\expandafter\xdef\csname label#1\endcsname{#2}}
\newcommand\getlabel[1]{\csname label#1\endcsname}

\begin{document}
\begin{tikzpicture}
  \tikzset{mainstyle/.style={circle,draw,fill=gray!40,minimum size=20}}
  \def\xmin{1}
  \def\xmax{4}
  \def\ymin{1}
  \def\ymax{5}
  \def\lattconst{3.0}
  \foreach \x in {\xmin,...,\xmax}
    \foreach \y in {\ymin,...,\ymax}
    {
      \pgfmathtruncatemacro{\label}{\x - \xmax *  \y + \xmax * \ymax}
      \storelabel{\x-\y}{\label}
      %%%
      \pgfmathsetmacro{\xpos}{\lattconst*\x}
      \pgfmathsetmacro{\ypos}{\lattconst*\y}
      \node [mainstyle] (\x-\y) at (\xpos,\ypos) {\label};
    }
\end{tikzpicture}

Label of 3-4 is \getlabel{3-4}.

Label of 1-1 is \getlabel{1-1}.

Label of 4-5 is \getlabel{4-5}.

\end{document}

[Tex/LaTex] If-then-else inside TikZ graph

\ifthenelse is "normal" LaTeX code. Therefore you can not use this command inside a TikZ path specification. But since the node text is put in a normal TeX box you can use \ifthenelse inside the node text. So you can try

\documentclass[tikz,margin=5mm]{standalone}
\usetikzlibrary{graphs,graphs.standard,quotes}

\usepackage{ifthen}

\begin{document}
\begin{tikzpicture}[
  vertex/.style={circle,fill=blue!15,draw,minimum size=17pt,inner sep=0pt}
]
%See TikZ documentation! (Section 19, graphs)
\graph[circular placement, radius=4cm, group polar shift=(360/5:0),
         nodes={circle,draw,vertex}] {
    \foreach \x in {0,...,4} {
      \foreach \y in {\x,...,4} {
        \x --["\ifthenelse{\x=3 \OR \y=3 \OR \x=\y}{}{\x\y}",sloped] \y;
  }}};
\end{tikzpicture}
\end{document}

enter image description here

Or you can position the nodes inside the \graph and connect them outside. Then you can use \ifthenelse outside of a path specification. Note that the complete \draw paths are in the arguments of \ifthenelse.

\documentclass[tikz,margin=5mm]{standalone}
\usetikzlibrary{graphs,graphs.standard,quotes}

\usepackage{ifthen}

\begin{document}
\begin{tikzpicture}[
  vertex/.style={circle,fill=blue!15,draw,minimum size=17pt,inner sep=0pt}
]
%See TikZ documentation! (Section 19, graphs)
\graph[circular placement, radius=4cm, group polar shift=(360/5:0),
         nodes={circle,draw,vertex}] {\foreach \x in {0,...,4} \x;
};
\foreach \x in {0,...,4} {
  \foreach \y in {\x,...,4} {
    \ifthenelse{\x=3 \OR \y=3 \OR \x=\y}{\draw(\x)--(\y);}{\draw(\x)--node[auto,sloped]{\x\y}(\y);}
}}
\end{tikzpicture}
\end{document}

The result is the same as above.

In the pgfmanual you can also find \pgfextra as a possibilty to suspend temporarly the path construction and do some other things like \ifthenelse. Here is a simple example where the filling color depends on the counter:

\documentclass[tikz,margin=5mm]{standalone}
\newcommand\mycolor{blue!15}
\usepackage{ifthen}
\begin{document}
    \begin{tikzpicture}[
        vertex/.style={circle,draw,minimum size=17pt,inner sep=0pt}
      ]
  \foreach \i in {0,...,4}{
    \path(0,0)\pgfextra{\ifthenelse{\i=2}{\def\mycolor{red!15}}{}}
      (90+\i*72:1)node[vertex,fill=\mycolor]{\i};}
\end{tikzpicture}
\end{document}

This results in

enter image description here

But AFAIK this does not work inside a \graph command.

Update:

Solutions without package \ifthen based on a suggestion of @marmot in a comment:

\documentclass[tikz,margin=5mm]{standalone}
\usetikzlibrary{graphs,graphs.standard,quotes}

\begin{document}
\begin{tikzpicture}[
  vertex/.style={circle,fill=blue!15,draw,minimum size=17pt,inner sep=0pt}
]
%See TikZ documentation! (Section 19, graphs)
\graph[circular placement, radius=4cm, group polar shift=(360/5:0),
         nodes={circle,draw,vertex}] {
    \foreach \x in {0,...,4} {
      \foreach \y 
        [evaluate=\y as \z using {int(ifthenelse(\x==3 || \y==3 || \x==\y,1,0))}]
        in {\x,...,4} {
        \x --["\ifnum \z=0 {\x\y}\fi",sloped] \y;
  }}};
\end{tikzpicture}
\end{document}

\documentclass[tikz,margin=5mm]{standalone}
\usetikzlibrary{graphs,graphs.standard,quotes}

\begin{document}
\begin{tikzpicture}[
  vertex/.style={circle,fill=blue!15,draw,minimum size=17pt,inner sep=0pt}
]
%See TikZ documentation! (Section 19, graphs)
\graph[circular placement, radius=4cm, group polar shift=(360/5:0),
         nodes={circle,draw,vertex}] {\foreach \x in {0,...,4} \x;
};
\foreach \x in {0,...,4} {
  \foreach \y 
    [evaluate=\y as \z using {int(ifthenelse(\x==3 || \y==3 || \x==\y,1,0))}]
    in {\x,...,4} {
      \ifnum \z=1
        \draw(\x)--(\y);
      \else 
        \draw(\x)--node[auto,sloped]{\x\y}(\y);
      \fi
}}
\end{tikzpicture}
\end{document}

The result is the same as in the first picture.

Best Answer

Related Solutions

[Tex/LaTex] How to dynamically name and store macros/variables in \foreach in TikZ for later use

[Tex/LaTex] If-then-else inside TikZ graph

Related Question