modelo_binomial.pgf

\def\hscale{-1.2}%
\def\size{25}%
\def\bzero{4}%
\def\bone{-2}%

\newcommand*{\ListXYvalues}{0.5, 1, 1.5, 2, 2.5, 3, 3.5}%
\newcommand*\pgfplotsinvokeforeachmacro[1]{%
  \expandafter\pgfplotsinvokeforeach\expandafter{#1}}%

\tikzset{%
  declare function={
    binompf(\k,\n,\p)=\n!/(\k!*(\n-\k)!)*\p^\k*(1-\p)^(\n-\k);
  },
  declare function={
    eta(\x,\bzero,\bone)=1/(1+exp(\bzero+\bone*\x));
  },
  hplot/.style={ycomb, mark=o, samples at={0,1,...,20}},
  vplot/.style={
    xcomb, no marks,
    very thick, line cap=round,
  },
  >=stealth,
  cx/.style={fill=white, font=\footnotesize},
  pth/.style={draw, ->, color=darkgreen},
  halves/.style={samples=30, fill opacity=0.5, draw=none}
}%

\pgfplotsset{%
  my plot/.code args={#1}{%
    \addplot [
      vplot,
      restrict x to domain=-1:-0.005,
      samples at={0, 1, ..., \size},
      shift={(axis direction cs: #1, 0)},
    ] ({\hscale*binompf(x, \size, 1/(1+exp(\bzero+\bone*#1)))}, x);
  }
}%

\begin{tikzpicture}%
  \begin{axis}[
    clip = false,
    width=7cm, height=7cm,
    xlabel=$x$,
%     ylabel={$\text{E}(Y|x) = n\cdot p(x)$},
    ylabel={$y$},
    xmin=-0.25]

    \addplot[domain=0:3.75, samples=30, smooth, orange, very thick]
      (x, {\size*eta(x, \bzero, \bone)});
    \pgfplotsinvokeforeachmacro\ListXYvalues{
      \pgfplotsset{my plot={#1}}
    }

  \foreach \x in {0.5, 1, ..., 3.5}{
    \edef\temp{
      \noexpand
      \draw [dotted, thin, gray] (\x, 0) -- (\x, \size);
    }
    \temp
  }

  \path[draw] (2, 30)
    node {\small $Y|x \sim \text{binomial}(n, p(x))$}
    edge[<-, out=-90, in=180] (1.75, 12.5);

  \end{axis}

\end{tikzpicture}%