Mathematical manipulation of a pgf macro

Question

I am trying to draw a TikZ diagram that I would like to start counting from zero instead of one. I have adapted this answer for my needs.

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}[auto matrix/.style={matrix of nodes,
  draw,thick,inner sep=0pt,
  nodes in empty cells,column sep=-0.2pt,row sep=-0.2pt,
  cells={nodes={minimum width=1.9em,minimum height=1.9em,
   draw,very thin,anchor=center,fill=white,
   execute at begin node={%
   $\vphantom{x_|}\ifnum\the\pgfmatrixcurrentrow<4
     \ifnum\the\pgfmatrixcurrentcolumn<4
      {#1}^{\the\pgfmatrixcurrentrow}_{\the\pgfmatrixcurrentcolumn}
     \else 
      \ifnum\the\pgfmatrixcurrentcolumn=5
       {#1}^{\the\pgfmatrixcurrentrow}_{N}
      \fi
     \fi
    \else
     \ifnum\the\pgfmatrixcurrentrow=5
      \ifnum\the\pgfmatrixcurrentcolumn<4
       {#1}^{T}_{\the\pgfmatrixcurrentcolumn}
      \else
       \ifnum\the\pgfmatrixcurrentcolumn=5
        {#1}^{T}_{N}
       \fi 
      \fi
     \fi
    \fi  
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=14
     \cdots
    \fi
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=41
     \vdots
    \fi
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=44
     \ddots
    \fi$
    }
  }}}]
 \matrix[auto matrix=z,xshift=3em,yshift=3em](matz){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \matrix[auto matrix=y,xshift=1.5em,yshift=1.5em](maty){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \matrix[auto matrix=x](matx){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \draw[thick,-stealth] ([xshift=1ex]matx.south east) -- ([xshift=1ex]matz.south east)
  node[midway,below] {$D$};
 \draw[thick,-stealth] ([yshift=-1ex]matx.south west) -- 
  ([yshift=-1ex]matx.south east) node[midway,below] {joints};
 \draw[thick,-stealth] ([xshift=-1ex]matx.north west)
   -- ([xshift=-1ex]matx.south west) node[midway,above,rotate=90] {time};
\end{tikzpicture}
\end{document}

This code has the following output.

I would like the index to begin from zero. Something like this.

I tried using the calc package to subtract from the \the\pgfmatrixcurrentrow and the \the\pgfmatrixcurrentcolumn like $\the\pgfmatrixcurrentrow - 1 = \result$ but to no avail. Any help is greatly appreciated.

Thank you for the answer. Could you explain the purpose of the \relax? — Rashiq, May 02 '21 at 21:24
The \relax is a signal to TeX to stop scanning for an expression. \the\numexpr 3 + 2 + 1\relax gives 6 whereas \the\numexpr 3 + 2\relax + 1 gives 5 + 1. — Henri Menke, May 03 '21 at 06:23

score 6 · Accepted Answer · answered May 02 '21 at 19:25

You can use \pgfmathtruncatemacro to compute your desired numbers just before all the code into the matrix definition, and replace all \the\pgfmatrixcurrentrow and \the\pgfmatrixcurrentcolumn by your computed variables.

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}[auto matrix/.style={matrix of nodes,
  draw,thick,inner sep=0pt,
  nodes in empty cells,column sep=-0.2pt,row sep=-0.2pt,
  cells={nodes={minimum width=1.9em,minimum height=1.9em,
   draw,very thin,anchor=center,fill=white,
   execute at begin node={%
   \pgfmathtruncatemacro{\nrow}{\the\pgfmatrixcurrentrow-1}%
   \pgfmathtruncatemacro{\ncol}{\the\pgfmatrixcurrentcolumn-1}%
   $\vphantom{x_|}\ifnum\the\pgfmatrixcurrentrow<4
     \ifnum\the\pgfmatrixcurrentcolumn<4
      {#1}^{\nrow}_{\ncol}     
     \else 
      \ifnum\the\pgfmatrixcurrentcolumn=5
       {#1}^{\nrow}_{N}
      \fi
     \fi
    \else
     \ifnum\the\pgfmatrixcurrentrow=5
      \ifnum\the\pgfmatrixcurrentcolumn<4
       {#1}^{T}_{\ncol}
      \else
       \ifnum\the\pgfmatrixcurrentcolumn=5
        {#1}^{T}_{N}
       \fi 
      \fi
     \fi
    \fi  
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=14
     \cdots
    \fi
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=41
     \vdots
    \fi
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=44
     \ddots
    \fi$
    }
  }}}]
 \matrix[auto matrix=z,xshift=3em,yshift=3em](matz){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \matrix[auto matrix=y,xshift=1.5em,yshift=1.5em](maty){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \matrix[auto matrix=x](matx){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \draw[thick,-stealth] ([xshift=1ex]matx.south east) -- ([xshift=1ex]matz.south east)
  node[midway,below] {$D$};
 \draw[thick,-stealth] ([yshift=-1ex]matx.south west) -- 
  ([yshift=-1ex]matx.south east) node[midway,below] {joints};
 \draw[thick,-stealth] ([xshift=-1ex]matx.north west)
   -- ([xshift=-1ex]matx.south west) node[midway,above,rotate=90] {time};
\end{tikzpicture}
\end{document}

egreg · Answer 2 · 2021-05-03T20:30:10.780

Since these are integers, use \the\numexpr\pgfmatrixcurrentrow-1

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}[auto matrix/.style={matrix of nodes,
  draw,thick,inner sep=0pt,
  nodes in empty cells,column sep=-0.2pt,row sep=-0.2pt,
  cells={nodes={minimum width=1.9em,minimum height=1.9em,
   draw,very thin,anchor=center,fill=white,
   execute at begin node={%
   $\vphantom{x_|}\ifnum\the\pgfmatrixcurrentrow<4
     \ifnum\the\pgfmatrixcurrentcolumn<4
      {#1}^{\the\numexpr\pgfmatrixcurrentrow-1}_{\the\numexpr\pgfmatrixcurrentcolumn-1}
     \else 
      \ifnum\the\pgfmatrixcurrentcolumn=5
       \,{#1}^{\the\numexpr\pgfmatrixcurrentrow-1}_{N}
      \fi
     \fi
    \else
     \ifnum\the\pgfmatrixcurrentrow=5
      \ifnum\the\pgfmatrixcurrentcolumn<4
       {#1}^{T}_{\the\numexpr\pgfmatrixcurrentcolumn-1}
      \else
       \ifnum\the\pgfmatrixcurrentcolumn=5
        \,{#1}^{T}_{N}
       \fi 
      \fi
     \fi
    \fi  
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=14
     \cdots
    \fi
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=41
     \vdots
    \fi
    \ifnum\the\pgfmatrixcurrentrow\the\pgfmatrixcurrentcolumn=44
     \ddots
    \fi$
    }
  }}}]
 \matrix[auto matrix=z,xshift=3em,yshift=3em](matz){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \matrix[auto matrix=y,xshift=1.5em,yshift=1.5em](maty){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \matrix[auto matrix=x](matx){
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
  & & & & \\
 };
 \draw[thick,-stealth] ([xshift=1ex]matx.south east) -- ([xshift=1ex]matz.south east)
  node[midway,below] {$D$};
 \draw[thick,-stealth] ([yshift=-1ex]matx.south west) -- 
  ([yshift=-1ex]matx.south east) node[midway,below] {joints};
 \draw[thick,-stealth] ([xshift=-1ex]matx.north west)
   -- ([xshift=-1ex]matx.south west) node[midway,above,rotate=90] {time};
\end{tikzpicture}
\end{document}

I also added \, in the last column to avoid too much overlapping.

Mathematical manipulation of a pgf macro

2 Answers2