How to modify the direction of this arrow?

Question

I'm modifying this code to have an arrow as in the picture. I'm tried but unable to reach my goal. Please help me modify it! Thank you so much!

\documentclass[12pt]{extreport}
\usepackage[left = 1in, right = 1in, top = 0.7in, bottom = 0.7in]{geometry}
\usepackage{graphicx,latexsym,mathtools}
\usepackage{tikz,tkz-tab}

\begin{document}

\begin{tikzpicture}
\tkzTab
[lgt=5,espcl=3] 
{$x$/1, $f_\alpha'(x)$/1, $f_\alpha(x)$/3} 
{$0$, $\alpha-1$, $x^*(\alpha)$, $+\infty$} 
{,+,0,-,-,-,} 
{-/ $0$, +/ $f_\alpha(\alpha-1)$, -/ $0$ , -/ $-\infty$} 
\end{tikzpicture}

\end{document}

Answer 1

I think plain TikZ is not so difficult as OP complained ^^ What does plain mean? SIMPLE! Change [yscale=.8,xscale=1.4] as you wish!

\documentclass[tikz,border=5mm]{standalone}
\begin{document}
\begin{tikzpicture}[yscale=.8,xscale=1.4]
\draw[shift={(-.5,.5)}] (0,0) rectangle +(8,-5) 
(0,-1)--+(0:8) (0,-2)--+(0:8) (1,0)--+(-90:5);
\path
(0,0)    node{$x$}          % <<< line 1
++(0:1)  node{$0$}
++(0:2)  node{$\alpha -1$}
++(0:2)  node{$x^*(\alpha)$}
++(0:2)  node{$+\infty$}
(0,-1)   node{$f'_{\alpha}(x)$}         % <<< line 2
++(0:2)  node{$+$}
++(0:1)  node{$0$}
++(0:1)  node{$-$}
++(0:2)  node{$-$}
(0,-3)   node{$f_{\alpha}(x)$}          % <<< line 3
++(0:1)  node (A) {$0$}
++(0:2)  +(90:1) node (B) {$f_{\alpha}(\alpha -1)$}
++(0:2)  node (C) {$0$}
++(0:2)  +(-90:1) node (D) {$-\infty$}
;
\foreach \p/\q in {A/B,B/C,C/D}
\draw[-stealth,magenta] (\p)--(\q);
\end{tikzpicture}
\end{document}

Answer 2

I used the intermediate tab value command from page 33 of the manual

\tkzTabVal{2}{3}{0.5}{$x^*(\alpha)$}{0}

the {2}{3} refers to the column precedent and antecedent and 0.5 on the sloped line -- -- a second negative/descent/derivative is provided with the help of intermediate entries-- these intermediate entries are not shown with a column heading of - since the continuous down slope shows that anyway

The manual is at -- http://ftp.cc.uoc.gr/mirrors/CTAN/macros/latex/contrib/tkz/tkz-tab/doc/tkz-tab-screen.pdf

\documentclass[12pt]{extreport}
\usepackage[left = 1in, right = 1in, top = 0.7in, bottom 
= 0.7in]{geometry}
\usepackage{graphicx,latexsym,mathtools}
\usepackage{tikz,tkz-tab}

\begin{document}

\begin{tikzpicture}

\newcommand*{\va}{\colorbox{red!50} {$\scriptscriptstyle 
V_a$}}
\newcommand*{\vb}{\colorbox{blue!50} {$\scriptscriptstyle 
V_b$}}
\newcommand*{\vbo}{\colorbox{blue!50} 
{$\scriptscriptstyle 
V_{b1}$}}
\newcommand*{\vbt}{\colorbox{yellow!50} 
{$\scriptscriptstyle 
V_{b2}$}}
\newcommand*{\vc}{\colorbox{gray!50} {$\scriptscriptstyle 
V_c$}}
\newcommand*{\vd}{\colorbox{magenta!50} 
{$\scriptscriptstyle 
V_d$}}
\newcommand*{\ve}{\colorbox{orange!50} 
{$\scriptscriptstyle 
V_e$}}
\tkzTabInit[color,
colorT = yellow!20,
colorC = red!20,
colorL = green!20,
colorV = lightgray!20,
lgt = 3,
espcl = 4]%
{$x$/1, $f_\alpha'(x)$/1, $f_\alpha(x)$/3}%
{$0$, $\alpha-1$,$+\infty$} 
\tkzTabLine{ ,+,0,-,-,, }
\tkzTabVar{-/ $0$, +/ $f_\alpha(\alpha-1)$,-/ $-\infty$}%
\tkzTabVal{2}{3}{0.5}{$x^*(\alpha)$}{0}
\end{tikzpicture}
\end{document}

Answer 3

I have found other solutions too. Just post here for future reference.

\usetikzlibrary{calc,angles,quotes}
\begin{document}
\begin{tikzpicture}
\tkzTabInit[lgt=1.5,espcl=3,deltacl=0.5]
{$x$/.6, $f_{\alpha}'(x)$/.6, $f_{\alpha}(x)$/2.5}
{$0$,$\alpha-1$,$x^*(\alpha)$,$+\infty$}
\tkzTabLine{,+,z,-,-,-,}
\draw
($(N12)!0.5!(N13)$) node (A){$0$}
(N22) node[below] (B) {$f_{\alpha}(\alpha-1)$}
($(N32)!0.5!(N33)$) node (C) {$0$}
(N43) node[above] (D) {$-\infty$};
\draw[-stealth] (A)--(B);
\draw[-stealth] (B)--(C);
\draw[-stealth] (C)--(D);
\end{tikzpicture}

\begin{tikzpicture}[>=stealth,line join=round,line cap=round,font=\footnotesize,scale=1]
\tkzTabInit[nocadre=false,lgt=1.5,espcl=2,deltacl=0.5]{$x$/.7 ,$f'_\alpha(x)$/.7,$f_\alpha(x)$/2}
{ $0$ , $\alpha-1$ ,$x^*(\alpha)$ , $+\infty$}
\tkzTabLine{ , + , $0$ , - ,-, - , }
\draw
($(N13)!0.5!(N12)$) node(A){$0$}
(N22) node[below] (B){$f_\alpha(\alpha-1)$ }
($(N32)!0.5!(N33)$) node (C){$0$}
(N43) node[above](D){$-\infty$};
\draw[->=stealth] (A)--(B) ;
\draw[->=stealth](B)--(C)--(D);
\end{tikzpicture}