我怎样才能缩小图表？

Question

如何在保持纵横比不变的情况下缩小图形？

\documentclass[10pt]{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\begin{document}
\begin{tikzpicture}[
  declare function={
    func(\x)= (\x >0) * (1+2^x)   +  (\x <= 0) * (-x^2-x+2)
   ;
  }
]
\begin{axis}[
  axis x line=middle, axis y line=middle,
  axis line style={thick},
  tick style={black, thick},
  ymin=-2, ymax=5, ytick={-1,4}, ylabel=$y$,
  xmin=-4, xmax=4, xtick={-3,-1,1,3}, xlabel=$x$,
  domain=-4:3,samples=101,
]

\addplot [blue,thick] {func(x)};
\node at (-3.2, 2) {$\math{y=-x^2-ax+b}$};
\node at (2.8, 3.5) {$\math{y=2^x+1}$};
\begin{scriptsize}
\draw [fill=black] (0.,2.05) circle (2.2pt);
\draw[color=ffffff] (0.21,1.8) node {$2$};
\end{scriptsize}
\end{axis}
\end{tikzpicture}
\end{document}

Answer 1

我必须进行大量修正和假设才能编译您的代码。当然，请删除\math包装器。

为图表设置明确宽度的一种方法是将其包裹在\resizebox包装器（由graphicx包提供）或\scalebox包装器（由adjustbox包提供）中。

\documentclass[10pt]{article}
\usepackage{pgfplots,xcolor,graphicx}
\pgfplotsset{compat=1.15}
\begin{document}

\newcommand\mygraph{%
\begin{tikzpicture}[
  declare function={
    func(\x)= (x > 0) * (1+2^x)   +  (x <= 0) * (-x^2-x+2);
  }
]
\begin{axis}[
  axis x line=middle, axis y line=middle,
  axis line style={thick},
  tick style={black, thick},
  ymin=-2, ymax=5, ytick={-1,4},      ylabel=$y$,
  xmin=-4, xmax=4, xtick={-3,-1,1,3}, xlabel=$x$,
  domain=-4:3,samples=101,
]
\addplot [blue,thick] {func(x)};
\node at (-2.4, 2.4) {$y=-x^2-x+2$};
\node at ( 2.5, 3.5) {$y=2^x+1$};
\begin{scriptsize}
\draw [fill=black] (0.,2.05) circle (2.2pt);
\draw[color=black] (0.21,1.8) node {$2$};
\end{scriptsize}
\end{axis}
\end{tikzpicture}}

\noindent
\mygraph % native size
\quad
\resizebox{4cm}{!}{\mygraph} % choose an explicit width, say, 4cm

\end{document}

Answer 2

正如我在评论中所说：

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15} % recent is 1.18

\begin{document}
    \begin{tikzpicture}[
declare function = {func(\x)=(\x>0)*(2^\x +1) + (\x<=0)*(-\x^2-\x+2 + 2);}
                        ]
\begin{axis}[
    width=6cm,  % define width of image according to your needs
  axis lines=middle,
  axis line style={thick},
  tick style={black, thick},
  ymin=-2, ymax=5, ytick={-1, 2,4},      ylabel=$y$,
  xmin=-4, xmax=4, xtick={-3,-1,1,3}, xlabel=$x$,
  ticklabel style={font=\footnotesize},
  domain=-4:3, samples=301
            ]
\addplot +[thick, no marks] {func(x)};
\addplot  [black,mark=*] coordinates {(0,2)};

\node[left]  at (0, 3) {$y=-x^2-ax+b$};
\node[right] at (1, 2) {$y=2^x+1$};

\end{axis}
    \end{tikzpicture}
\end{document}