使用 TikZ 创建概率直方图

Question

我正在尝试创建一个概率直方图，这是它的当前状态

\documentclass[oneside,english]{amsart}
\usepackage{tikz}
\usepackage{pgfplots}

\begin{document}

\begin{tikzpicture}
\begin{axis}[    ybar,    ymin=0,    ymax=0.6,    xlabel={$k$},    ylabel={$\mathbb{P} 
(Z_2=k)$},    xtick={0,...,7},    ytick={0,0.2,...,0.6},    bar width=0.8,    axis 
lines=left,    width=8cm,    height=8cm,    enlarge x limits=0.1,    enlarge y 
limits=0.1,    ]
\addplot+[ybar interval,mark=no] plot coordinates {(-0.5, 0.5) (0.5, 0.25) (1.5, 0.125) 
(2.5, 0.0625) (3.5, 0.03125) (4.5, 0.015625) (5.5, 0.0078125) (6.5, 0.00390625) (7.5, 
0.001953125)};
\end{axis}
\end{tikzpicture}
\end{document}

有没有办法将 y 轴向下移动，使条形图从水平轴发出？我还想将 y 轴稍微向右移动，使其与第一个矩形的左侧重合。

Answer 1

像这样？

您需要进行 enlarge y limits相应设置：

\documentclass[oneside,english]{amsart}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}

\begin{tikzpicture}
\begin{axis}[width=8cm,    height=8cm,
    axis lines=left,   
    ybar,    
    bar width=1, 
    xlabel={$k$},    ylabel={$\mathbb{P}(Z_2=k)$},    
    xtick={0,...,8},    
    enlarge x limits=0.1,    
    enlarge y limits={0.1, upper}  % <----
            ]
\addplot +[ybar interval]
            plot coordinates {  (-0.5,0.5)      (0.5,0.25)          (1.5,0.125)
                                (2.5,0.0625)    (3.5,0.03125)       (4.5,0.015625) 
                                (5.5,0.0078125) (6.5,0.00390625)    (7.5,0.001953125)};
\end{axis}
\end{tikzpicture}
\end{document}

附录：
您可以在表中收集图表的数据，其中还定义了xticks。通过此更改，图表代码会更简单、更简短：

\documentclass[oneside,english]{amsart}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}
\begin{tikzpicture}
\begin{axis}[width=8cm, height=8cm,
    axis lines=left,
    ybar,
    bar width=1,
    xlabel={$k$},    ylabel={$\mathbb{P}(Z_2=k)$},
    ticklabel style = {font=\footnotesize},
    xtick=data,
    enlarge x limits=0.1,
    ymax=0.55
            ]
\addplot table[y index=1]  {1   0.5
                            2   0.25
                            3   0.125
                            4   0.0625
                            5   0.03125
                            6   0.015625
                            7   0.0078125
                            8   0.00390625
                            9   0.001953125
                            };
\end{axis}
    \end{tikzpicture}
\end{document}

图表与之前相同。