%%%------------------------------------------------------------------------------------------------------------
\begin{tikzpicture}
%% a two-layer neural network
\begin{scope}
{
\draw [->,thick] (-1.8,0) -- (1.8,0);
\draw [->,thick] (0,0) -- (0,2);
\node [anchor=south] (heng1) at (1.6,-0.35) {\scriptsize{$x$}};
\node [anchor=south] (zong1) at (-0.2,1.6) {\scriptsize{$y$}};
\draw [-] (-0.05,1) -- (0.05,1);
\node [anchor=east,inner sep=1pt] (label1) at (0,1) {\tiny{1}};
\node [anchor=south east,inner sep=1pt] (label2) at (0,0) {\tiny{0}};
\node [anchor=south east,inner sep=1pt] (labela) at (0.2,-0.5) {\small{(a)}};
}
{\node [anchor=north west,align=left] (wblabel) at (-2,2) {\scriptsize{\ $w_{11}=1$}\\[-0ex] \scriptsize{\ $b_1=0$}};}
{\draw [-,very thick,ublue,domain=-1.5:1.5,samples=100] plot (\x,{1/(1+exp(-2*\x))});}
\end{scope}
%---------------------------------------------------------------------------------------------
\begin{scope}[xshift=1.6in]
{
\draw [->,thick] (-1.8,0) -- (1.8,0);
\draw [->,thick] (0,0) -- (0,2);
\draw [-] (-0.05,1) -- (0.05,1);
\node [anchor=south] (heng1) at (1.6,-0.35) {\scriptsize{$x$}};
\node [anchor=south] (zong1) at (-0.2,1.6) {\scriptsize{$y$}};
\node [anchor=east,inner sep=1pt] (label1) at (0,1) {\tiny{1}};
\node [anchor=south east,inner sep=1pt] (label2) at (0,0) {\tiny{0}};
\node [anchor=south east,inner sep=1pt] (labelb) at (0.2,-0.5) {\small{(b)}};
}
{\node [anchor=north west,align=left] (wblabel) at (-2,2) {{\scriptsize{\ $w_{11}=10$}}\\[-0ex] \scriptsize{\ $b_1=0$}};}
{\draw [-,very thick,ublue,domain=-1.5:1.5,samples=100] plot (\x,{1/(1+exp(-4*\x))});}
\end{scope}
%-----------------------------------------------------------------------------------------------
\begin{scope}[xshift=3.2in]
{
\draw [->,thick] (-1.8,0) -- (1.8,0);
\draw [->,thick] (0,0) -- (0,2);
\node [anchor=south] (heng1) at (1.6,-0.35) {\scriptsize{$x$}};
\node [anchor=south] (zong1) at (-0.2,1.6) {\scriptsize{$y$}};
\draw [-] (-0.05,1) -- (0.05,1);
\node [anchor=east,inner sep=1pt] (label1) at (0,1) {\tiny{1}};
\node [anchor=south east,inner sep=1pt] (label2) at (0,0) {\tiny{0}};
\node [anchor=south east,inner sep=1pt] (labelc) at (0.2,-0.5) {\small{(c)}};
}
{\node [anchor=north west,align=left] (wblabel) at (-2,2) {{\scriptsize{\ $w_{11}=100$}}\\[-0ex] \scriptsize{\ $b_1=0$}};}
{\draw [-,very thick,ublue,rounded corners=0.1em] (-1.5,0) -- (0,0) -- (0,1) -- (1.5,1);}
\end{scope}
\end{tikzpicture}
%%%------------------------------------------------------------------------------------------------------------