Individual row and column spacing in matrix environment

Question

I know that one can change the row and column separation in the \matrix command with row sep, respectively column sep. But how do one change the separation for a specific row or column only?

That is; having different spacing between between different rows? Also, how do one do the same for column spacing?

\documentclass{standalone}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \matrix[column sep=5mm, row sep=5mm]
    {
        % Row 1
        \node {1:1};&\node {1:2};&\node {1:3};&\node {1:4};;\\
        % Row 2
        \node {2:1};&\node {2:2};&\node {2:3};&\node {2:4};\\
        % Row 3
        \node {3:1};&\node {3:2};&\node {3:3};&\node {3:4};\\
    };
\end{tikzpicture}
\end{document}

Answer 1

You can set the separation to zero; then use &[<width>] in the first row for column separation and \\[<width>] for row separation.

\documentclass{standalone}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
  \matrix[column sep=0mm, row sep=0mm]{
    % Row 1
    \node {1:1}; &[5mm] \node {1:2}; &[10mm] \node {1:3}; &[10mm] \node {1:4}; \\[5mm]
    % Row 2
    \node {2:1}; &      \node {2:2}; &       \node {2:3}; &       \node {2:4}; \\[10mm]
    % Row 3
    \node {3:1}; &      \node {3:2}; &       \node {3:3}; &       \node {3:4}; \\
  };
\end{tikzpicture}

\end{document}

Answer 2

ROW SEPARATION

For the row spacing, instead of specifying a matrix-wide row sep, use the optional argument to \\ to accomplish row specific skips.

\documentclass{standalone}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \matrix[column sep=5mm]
    {
        % Row 1
        \node {1:1};&\node {1:2};&\node {1:3};&\node {1:4};;\\[5mm]
        % Row 2
        \node {2:1};&\node {2:2};&\node {2:3};&\node {2:4};\\[10mm]
        % Row 3
        \node {3:1};&\node {3:2};&\node {3:3};&\node {3:4};\\
    };
\end{tikzpicture}
\end{document}

Alternately, you can keep a default row sep and specify the deviation from it:

\documentclass{standalone}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \matrix[column sep=5mm, row sep=5mm]
    {
        % Row 1
        \node {1:1};&\node {1:2};&\node {1:3};&\node {1:4};;\\
        % Row 2
        \node {2:1};&\node {2:2};&\node {2:3};&\node {2:4};\\[5mm]
        % Row 3
        \node {3:1};&\node {3:2};&\node {3:3};&\node {3:4};\\
    };
\end{tikzpicture}
\end{document}

---

COLUMN SEPARATION

As to the issue of column separation, I know of no easy way to accomplish this. In the particular example provided by the OP, the column gaps are all integer multiples of each other. If that were always the case, one can just add blank columns:

\documentclass{standalone}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \matrix[column sep=5mm, row sep=5mm]
    {
        % Row 1
        \node {1:1};&\node {1:2};&&\node {1:3};&\node {1:4};;\\
        % Row 2
        \node {2:1};&\node {2:2};&&\node {2:3};&\node {2:4};\\[5mm]
        % Row 3
        \node {3:1};&\node {3:2};&&\node {3:3};&\node {3:4};\\
    };
\end{tikzpicture}
\end{document}

But I presume that is too much to hope for. The best I could do for the general case is provide the \knode macro that has an optional kern built in.

\documentclass{standalone}
\usepackage{tikz}
\newcommand\knode[2][0]{\node{#2\kern#1mm}}
\begin{document}
\begin{tikzpicture}
    \matrix[column sep=5mm, row sep=5mm]
    {
        % Row 1
        \node {1:1};&\knode[5]{1:2};&\node {1:3};&\node {1:4};;\\
        % Row 2
        \node {2:1};&\knode[5]{2:2};&\node {2:3};&\node {2:4};\\[5mm]
        % Row 3
        \node {3:1};&\knode[5]{3:2};&\node {3:3};&\node {3:4};\\
    };
\end{tikzpicture}
\end{document}