Fine point with Tkz-Tab

Question

I'd like to do this with the package Tkz-Tab :

But I can't seem to find the option to insert the double vertical bars that I added in red to the image.

Does someone know how to do this ?

This is the code I used to draw this table :

\documentclass{article}
\usepackage{tkz-tab}
\begin{document}
\begin{tikzpicture}
  \tkzTabInit[espcl=1.7]{$x$/0.6,$f''(x)$/0.6,$f'$/1.5,$f'(x)$/0.6,$f$/2}{%
    $-\infty$,$-1$,$0$,$\alpha$,$1$,$+\infty$}
  \tkzTabLine{,+,d,+,d,,-,,d,+,}
  \tkzTabVar{-/{$-\infty$},R,+D+/{$+\infty$}/{$+\infty$},R,-C/{$-2$},+/{$-1$}}
  \tkzTabIma{1}{3}{2}{$0$}
  \tkzTabIma{3}{5}{4}{$0$}
  \tkzTabLine{,-,d,+,d,+,z,-,d,-,}
  \tkzTabVar{+/{$+\infty$},-C/{$0$},R,+/{$f(\alpha)$},R,-/{$-\infty$}}
  \tkzTabIma{2}{4}{3}{$1$}
  \tkzTabIma{4}{6}{5}{$0$}
\end{tikzpicture}
\end{document}

Thanks for any help.

Answer 1

As with all my packages, you can use Tikz at any time. Here you just have to use the help option to find out all the nodes (coordinates) I use.

\documentclass{article}
\usepackage{tkz-tab}
\begin{document}
\begin{tikzpicture}
  \tkzTabInit[espcl=1.7,help]{$x$/0.6,$f''(x)$/0.6,$f'$/1.5,$f'(x)$/0.6,$f$/2}{%
    $-\infty$,$-1$,$0$,$\alpha$,$1$,$+\infty$}
  \tkzTabLine{,+,d,+,d,,-,,d,+,}
  \tkzTabVar{-/{$-\infty$},R,+D+/{$+\infty$}/{$+\infty$},R,-C/{$-2$},+/{$-1$}}
  \tkzTabIma{1}{3}{2}{$0$}
  \tkzTabIma{3}{5}{4}{$0$}
  \tkzTabLine{,-,d,+,d,+,z,-,d,-,}
  \tkzTabVar{+/{$+\infty$},-C/{$0$},R,+/{$f(\alpha)$},R,-/{$-\infty$}}
  \tkzTabIma{2}{4}{3}{$1$}
  \tkzTabIma{4}{6}{5}{$0$}
\end{tikzpicture}
\end{document}

We obtain this

Then we use TikZ:

\documentclass{article}
\usepackage{tkz-tab}
\begin{document}
\begin{tikzpicture}
  \tkzTabInit[espcl=1.7]{$x$/0.6,$f''(x)$/0.6,$f'$/1.5,$f'(x)$/0.6,$f$/2}{%
    $-\infty$,$-1$,$0$,$\alpha$,$1$,$+\infty$}
  \tkzTabLine{,+,d,+,d,,-,,d,+,}
  \draw[double style,color=red](N22) --(N23);
  \draw[double style,color=red](N34) --(N35);
  \draw[double style,color=red](N54) --(N55);
  \tkzTabVar{-/{$-\infty$},R,+D+/{$+\infty$}/{$+\infty$},R,-C/{$-2$},+/{$-1$}}
  \tkzTabIma{1}{3}{2}{$0$}
  \tkzTabIma{3}{5}{4}{$0$}
  \tkzTabLine{,-,d,+,d,+,z,-,d,-,}
  \tkzTabVar{+/{$+\infty$},-C/{$0$},R,+/{$f(\alpha)$},R,-/{$-\infty$}}
  \tkzTabIma{2}{4}{3}{$1$}
  \tkzTabIma{4}{6}{5}{$0$}
\end{tikzpicture}
\end{document}