Hello,
The third column of matrix is not centered vertically and horizontally.
thank you,
Fabrice


\setupbodyfont[pagella,11pt]

\definemathmatrix
  [pmatrix]
  [left={\left(\,},right={\,\right)}]

\define[3]\coef{\math{#1_{#2, #3}}\autoinsertnextspace}

\startsetups[table:initialize]
\setupTABLE[offset=0.8ex,width=0.25\textwidth]
\setupTABLE[row][first]
           [background=color,backgroundcolor=lightgray]
\setupTABLE[start][align={middle,lohi}]
\stopsetups

\starttext

{\bf Matrices particulières}

\startlinecorrection[blank]

\startmidaligned

\switchtobodyfont[10pt]

\bTABLE[setups=table:initialize]

  \bTR
    \bTD {\bf Matrice ligne} \\ Dimension \math{\left(1\times p\right)}
\eTD
    \bTD {\bf Matrice colonne} \\ Dimension \math{\left(n\times 1\right)}
\eTD
    \bTD {\bf Matrice carrée} \\ Dimension \math{\left(n\times n\right)}
\eTD
    \bTD {\bf Matrice unité \math{\bi I_n}} \\ Dimension
\math{\left(n\times n\right)}    \eTD
  \eTR

  \bTR
    \bTD \startformula
         \startpmatrix
           \NC \coef{a}{1}{1} \NC \coef{a}{1}{2} \NC \dots \NC
\coef{a}{1}{p}
         \stoppmatrix
         \stopformula
    \eTD
    \bTD \startformula
         \startpmatrix
           \NC \coef{a}{1}{1} \NR
           \NC \coef{a}{2}{1} \NR
           \NC    \dots       \NR
           \NC \coef{a}{n}{1}
         \stoppmatrix
         \stopformula
    \eTD
    \bTD \startformula
         \startpmatrix
        \NC \coef{a}{1}{1} \NC \coef{a}{1}{2} \NC \dots \NC
\coef{a}{1}{n}\NR
        \NC \coef{a}{2}{1} \NC \coef{a}{2}{2} \NC \dots \NC
\coef{a}{2}{n}\NR
        \NC \dots          \NC \dots          \NC \dots \NC \dots \NR
        \NC \coef{a}{n}{1} \NC \coef{a}{n}{2} \NC \dots \NC \coef{a}{n}{n}
         \stoppmatrix
         \stopformula
    \eTD
    \bTD \startformula
         \startpmatrix
         \NC 1 \NC 0 \NC \dots \NC 0 \NR
         \NC 0 \NC 1 \NC \dots \NC 0 \NR
         \NC \dots \NC \dots \NC \dots \NC \dots \NR
         \NC 0 \NC 0 \NC \dots \NC 1
         \stoppmatrix
         \stopformula
    \eTD
  \eTR

\eTABLE

\stopmidaligned

\stoplinecorrection

\stoptext