figure1-3-a-in_out_neural_network.tex

\documentclass[border = 0.2cm]{standalone}
 
% Required package
\usepackage{tikz}
\usepackage{medl_colors}
\begin {document}
 
% Input layer neurons'number
\newcommand{\inputnum}{8} 
 
% Hidden layer neurons'number
\newcommand{\hiddennum}{9}  

% Total Hidden layers
\newcommand{\hiddenlayers}{3}   
 
% Output layer neurons'number
\newcommand{\outputnum}{4} 
 
\begin{tikzpicture}
 
% Input Layer
\foreach \i in {1,...,\inputnum}
{
    \node[greenshape, circle, draw, minimum size = 6mm] (Input-\i) at (0,-\i) {};
}

\node[above of=Input-1, node distance=1cm] (AInputLayer) {{\Huge Input layer}};
 
% Hidden Layer
\foreach \i in {1,...,\hiddenlayers}
{
    \foreach \j in {1,...,\hiddennum}
    {
        \node[blueshape, circle, draw, minimum size = 6mm, yshift=(\hiddennum-\inputnum)*5 mm ] (Hidden-\i\j) at (5*\i,-\j) {};
    }
    \node[above of=Hidden-\i1, node distance=1cm] (AHiddenLayer\i) {{\Huge Layer \i}};
}
 
% Output Layer
\foreach \i in {1,...,\outputnum}
{
    \node[redshape, circle, draw, minimum size = 6mm, yshift=(\outputnum-\inputnum) * 5mm ] (Output-\i) at (20,-\i) {};
}

\node[above of=Output-1, node distance=1.4cm] (AOutputLayer) {{\Huge Output layer}};

% Connect neurons In-Hidden
\foreach \i in {1,...,\inputnum}
{
    \foreach \j in {1,...,\hiddennum}
    {
      \draw[line] (Input-\i) -- (Hidden-1\j);   
    }
} 

%\foreach \x[evaluate=\x as \evalx using int(\x+1)]

% Connect neurons between hidden layers
\foreach \i [evaluate=\i as \in using int(\i+1) ] in {1,2}
{
    \foreach \j  in {1,...,\hiddennum}
    {
        \foreach \k  in {1,...,\hiddennum}
        {
            \draw[line] (Hidden-\i\j) -- (Hidden-\in\k);
        }
    }
} 

% Connect neurons Hidden-Out
\foreach \i in {1,...,\hiddennum}
{
    \foreach \j in {1,...,\outputnum}
    {
      \draw[line] (Hidden-\hiddenlayers\i) -- (Output-\j);   
    }
} 

% Outputs
\foreach \i in {1,...,\outputnum}
{            
    \draw[-Triangle, thickline, shorten <=1pt] (Output-\i) -- ++(1,0)
        node[right]{};
}

\end{tikzpicture}
 
\end {document}