Homogeneous spacing for matrix elements

Question

can somebody tell me how to get homogeneous spacing between the elements of my matrix? Here is the code I'm using but it is not working as I was expecting.

\documentclass[12pt]{scrartcl}  
\usepackage{amsmath,tikz}
\usepackage{tabstackengine}
\usetikzlibrary{matrix}
\setcounter{MaxMatrixCols}{20} 

\begin{document}

\begin{equation}
\fixTABwidth{T}
\begin{tikzpicture}
\matrix (m) [baseline=(current bounding box.center),matrix of math nodes,nodes in empty cells,right delimiter={]},left delimiter={[} ]
{-4 & 1 & 0 & 0 & .. & 0 & 1 & 0 & 0 & 0 & 0 & ... &  & &&&&\\
1 & -4 & 1 & 0 & .. & 0 & 0 & 1 & 0 & 0 & 0 & ... &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
1 & 0 & 0 & 0 & .. & 0 & -4 & 1 & 0 & 0 & 0&...&0&1&0&0&0&...\\
0 & 1 & 0 & 0 & .. & 0 &  1 & -4 & 1 & 0& 0&...&0&0&1&0&0&...\\      
0 & 0 & 1 & 0 & .. & 0 &  0 & 1 & -4 & 1& 0&...&0&0&0&1&0&...\\ 
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
0 & 0 & 0 & 0 & .. & 0 &  0 & 1 & 0 & 0& ...&0&1&-4&1&0&0&...\\      
0 & 0 & 0 & 0 & .. & 0 &  0 & 0 & 1 & 0& ...&0&0&1&-4&1&0&...\\} ;
\draw[line width=0.4mm, loosely dotted] (m-2-2)-- (m-7-7);
\draw[line width=0.4mm,loosely dotted] (m-2-3)-- (m-7-8);
\draw[line width=0.4mm,loosely dotted] (m-2-1)-- (m-7-6);
\draw[line width=0.4mm,loosely dotted] (m-2-8)-- (m-7-14);
\draw[line width=0.4mm,loosely dotted] (m-9-8)-- (m-14-13);
\draw[line width=0.4mm,loosely dotted] (m-9-9)-- (m-14-14);
\draw[line width=0.4mm,loosely dotted] (m-9-10)-- (m-14-15);
\draw[line width=0.4mm,loosely dotted] (m-9-3)-- (m-14-8);
\end{tikzpicture}
\end{equation}

\end{document}

But it looks like this: And I see that the spacing between neighbouring elements is not the same.

I'd appreciate any suggestion!

Answer 1

You can achieve required spacing by adjusting the values of column sep of matrix and text width of node. See an example below.

\documentclass{scrartcl}  
\usepackage{tikz}
\usetikzlibrary{matrix}

\begin{document}

\begin{tikzpicture}
\matrix (m) [baseline=(current bounding box.center),matrix of math nodes,
column sep=0pt, nodes={text width=1.7em, align=right, anchor=east},
nodes in empty cells,right delimiter={]},left delimiter={[} ]
{-4 & 1 & 0 & 0 & .. & 0 & 1 & 0 & 0 & 0 & 0 & ... &  & &&&&\\
1 & -4 & 1 & 0 & .. & 0 & 0 & 1 & 0 & 0 & 0 & ... &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
1 & 0 & 0 & 0 & .. & 0 & -4 & 1 & 0 & 0 & 0&...&0&1&0&0&0&...\\
0 & 1 & 0 & 0 & .. & 0 &  1 & -4 & 1 & 0& 0&...&0&0&1&0&0&...\\      
0 & 0 & 1 & 0 & .. & 0 &  0 & 1 & -4 & 1& 0&...&0&0&0&1&0&...\\ 
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
&    &   &   &    &   &   &   &   &   &   &     &  & &&&&\\
0 & 0 & 0 & 0 & .. & 0 &  0 & 1 & 0 & 0& ...&0&1&-4&1&0&0&...\\      
0 & 0 & 0 & 0 & .. & 0 &  0 & 0 & 1 & 0& ...&0&0&1&-4&1&0&...\\} ;
\draw[line width=0.4mm, loosely dotted] (m-2-2)-- (m-7-7);
\draw[line width=0.4mm,loosely dotted] (m-2-3)-- (m-7-8);
\draw[line width=0.4mm,loosely dotted] (m-2-1)-- (m-7-6);
\draw[line width=0.4mm,loosely dotted] (m-2-8)-- (m-7-14);
\draw[line width=0.4mm,loosely dotted] (m-9-8)-- (m-14-13);
\draw[line width=0.4mm,loosely dotted] (m-9-9)-- (m-14-14);
\draw[line width=0.4mm,loosely dotted] (m-9-10)-- (m-14-15);
\draw[line width=0.4mm,loosely dotted] (m-9-3)-- (m-14-8);
\end{tikzpicture}

\end{document}

Answer 2

A little bit modified @nidhin answer (+1) ... Differences are in

• nodes style
• columns and rows spacing
• drawing dotted lines between nodes

\documentclass{scrartcl}
\usepackage{tikz}
\usetikzlibrary{matrix}

\begin{document}
    \begin{tikzpicture}[every path/.style = {thick, loosely dotted}]
\matrix (m) [matrix of math nodes,
             nodes in empty cells,
             nodes={text width=1.2em, minimum height=2ex,
                    inner sep=0pt, align=right, anchor=south},
             right delimiter={]},left delimiter={[},
             column sep=1pt,
             column 5/.style  = {column sep=-0.3em},
             row 14 column 12/.style = {nodes={text width=0.5em}},
             row 15 column 12/.style = {nodes={text width=0.5em}},
             column 12/.style = {column sep=-0.3em},
             row sep=1pt
             ]
{
-4  & 1  & 0 & 0 & ... & 0 & 1  & 0  & 0  & 0 & 0   & ... &   &    &    &   &   &   \\
1   & -4 & 1 & 0 & ... & 0 & 0  & 1  & 0  & 0 & 0   & ... &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
1   & 0  & 0 & 0 & ... & 0 & -4 & 1  & 0  & 0 & 0   & ... & 0 & 1  &  0 & 0 & 0 &...\\
0   & 1  & 0 & 0 & ... & 0 &  1 & -4 & 1  & 0 & 0   & ... & 0 & 0  &  1 & 0 & 0 &...\\
0   & 0  & 1 & 0 & ... & 0 &  0 & 1  & -4 & 1 & 0   & ... & 0 & 0  &  0 & 1 & 0 &...\\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
    &    &   &   &     &   &    &    &    &   &     &     &   &    &    &   &   &   \\
0   & 0  & 0 & 0 & ... & 0 &  0 & 1  & 0  & 0 & ... & 0   & 1 & -4 &  1 & 0 & 0 &...\\
0   & 0  & 0 & 0 & ... & 0 &  0 & 0  & 1  & 0 & ... & 0   & 0 & 1  & -4 & 1 & 0 &...\\
};
\draw   (m-2-1) -- (m-7-6.north);
\draw   (m-2-2) -- (m-7-7.north);
\draw   (m-2-3) -- (m-7-8.north);
\draw   (m-2-8) -- (m-7-14.north);
%
\draw   (m-9-3)-- (m-14-8.north);
\draw   (m-9-8) -- (m-14-13.north);
\draw   (m-9-9) -- (m-14-14.north);
\draw   (m-9-10)-- (m-14-15.north);
    \end{tikzpicture}
\end{document}