Finite Difference Method - explicit stencil in TikZ

fdm_explicit.tex

% Author: JE Touma (aitatanit@gmail.com)
% Finite difference method - explicit stencil
\documentclass{article}
\usepackage{tikz}
\usepackage{siunitx}

\usetikzlibrary{calc,decorations.pathmorphing,patterns}

\begin{document}

	
\begin{tikzpicture}[decorate]

 
 \filldraw[fill=red!80!white, draw=black,very thick] (5,5) circle (0.2cm);
 \draw[line width=0.4mm] (5,4.8) -- (5,2.2);
 \node at (5, 5.5) {$j, n+1$};
 

 \filldraw[fill=red!80!white, draw=black,very thick] (5,2) circle (0.2cm);
 \node at (5, 1.5) {$j, n$};
 \draw[line width=0.4mm] (4.8,2) -- (2.2,2);
 \filldraw[fill=red!80!white, draw=black,very thick] (2,2) circle (0.2cm);
  \node at (2, 1.5) {$j-1, n$};
 
 \draw[line width=0.4mm] (5.2,2) -- (7.8,2);
 \filldraw[fill=red!80!white, draw=black,very thick] (8,2) circle (0.2cm);
 \node at (8, 1.5) {$j+1, n$}; 
  
  
 %\draw[line width=0.4mm] (5,1.8) -- (5,-0.8);
 %\filldraw[fill=red!80!white, draw=black,very thick] (5,-1) circle (0.2cm);
 %\node at (5, -1.5) {$j, n-1$};  




 
\end{tikzpicture}
\end{document}