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Precisión de un trazado con TikZ

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Precisión de un trazado con TikZ

¿Por qué las líneas van más allá del eje de abscisas (círculos azules)?

   \documentclass[border=5mm]{standalone}
   \usepackage{pgfplots}
   \usepackage{amssymb}
   \begin{document}

   \pgfmathdeclarefunction{gauss}{1}{%
   \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/2)}%
     }

   \begin{tikzpicture}
   \begin{axis}[
   domain=-3:3,
   tickwidth=0.1cm,
   major tick style=black,
   axis lines=middle,
   axis line style =thick,
   axis line style={shorten >=-10pt, shorten <=-15pt},
   xlabel=$x$,ylabel=$y$,
   xtick={-2,...,2},ytick={0,0.1,0.2,0.3},
   xticklabels={,,,1,,,},
   yticklabels={,0.1,,},
   height=5cm, width=10cm,
   clip=false,
   axis on top,
   every axis x label/.style={
   at={(ticklabel* cs:1.03)},
   anchor=west},
   every axis y label/.style={
   at={(ticklabel* cs:1.1)},
   anchor=south},
   samples=1000,
   >=stealth,
   ]

  \pgfmathsetmacro\valueA{gauss(0.8)}
  \pgfmathsetmacro\valueB{gauss(-1.5)}
  \addplot [fill=orange!40, draw=none, domain=-1.5:0.8] {gauss(x)} \closedcycle;
  \draw [orange!80,thick] (axis cs:0.8,0) -- (axis cs:0.8,\valueA);
  \draw [orange!80,thick] (axis cs:-1.5,0) -- (axis cs:-1.5,\valueB);
  \addplot [ thick] {gauss(x)};
  \node[below,orange!80] at (axis cs:0.8,0){$b$};
  \node[below,orange!80] at (axis cs:-1.5,0){$a$};
  \node[below left] at (axis cs:0,0){$0$};
  \draw[orange,->](axis cs:2,0.4)--(axis cs:0.2,0.25);
  \draw[blue] (axis cs:0.8,0)  circle [radius=0.2cm];
  \draw[blue] (axis cs:-1.5,0)  circle [radius=0.2cm];
  \node[draw][orange,anchor=south west] at (axis cs:2,0.4)  {$P(a\leqslant X \leqslant b)$};
  \end{axis}
  \end{tikzpicture}
  \end{document}

ingrese la descripción de la imagen aquí

Respuesta1

Tu problema aquí es que tu xeje no pasa por el origen.(0,0)

Para solucionarlo, simplemente configúrelo yminen 0o menos.

La salida

ingrese la descripción de la imagen aquí

El código

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\usepackage{amssymb}
\begin{document}

\pgfmathdeclarefunction{gauss}{1}
{%
  \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/2)}%
}

\begin{tikzpicture}
  \begin{axis}
    [
      ymin=0, %%%%%%%%%%%%%%%%%%%%%%%%%%%  <--- just do this
      domain=-3:3,
      tickwidth=0.1cm,
      major tick style=black,
      axis lines=middle,
      axis line style =thick,
      axis line style={shorten >=-10pt, shorten <=-15pt},
      xlabel=$x$,ylabel=$y$,
      xtick={-2,...,2},ytick={0,0.1,0.2,0.3},
      xticklabels={,,,1,,,},
      yticklabels={,0.1,,},
      height=5cm, width=10cm,
      clip=false,
      axis on top,
      every axis x label/.style=
      {
        at={(ticklabel* cs:1.03)},
        anchor=west
      },
      every axis y label/.style=
      {
        at={(ticklabel* cs:1.1)},
        anchor=south
      },
      samples=100,
      >=stealth,
    ]

    \pgfmathsetmacro\valueA{gauss(0.8)}
    \pgfmathsetmacro\valueB{gauss(-1.5)}
    \addplot [fill=orange!40, draw=none, domain=-1.5:0.8] {gauss(x)} \closedcycle;
    \draw [orange!80,thick] (axis cs:0.8,0) -- (axis cs:0.8,\valueA);
    \draw [orange!80,thick] (axis cs:-1.5,0) -- (axis cs:-1.5,\valueB);
    \addplot [ thick] {gauss(x)};
    \node[below,orange!80] at (axis cs:0.8,0){$b$};
    \node[below,orange!80] at (axis cs:-1.5,0){$a$};
    \node[below left] at (axis cs:0,0){$0$};
    \draw[orange,->](axis cs:2,0.4)--(axis cs:0.2,0.25);
    \draw[blue] (axis cs:0.8,0)  circle [radius=0.2cm];
    \draw[blue] (axis cs:-1.5,0)  circle [radius=0.2cm];
    \node[draw][orange,anchor=south west] at (axis cs:2,0.4) {$P(a\leqslant X \leqslant b)$};
  \end{axis}
\end{tikzpicture}
\end{document}

Salud,

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