pgfplots 中的图例样式自定义

Question

我有这个条形图，我想做三件事：

1. 删除条形图中的数字，它们是重叠的（如果可能的话只保留一个，象征着两个条形图具有相同的值）；
2. 在图例的框架内输入“数据大小”，然后输入10KB和20KB的值；
3. 将 y 轴值更改为 28

我正在使用的代码：

\begin{tikzpicture}
\begin{axis}[
ybar,
enlargelimits=0.3,
legend  style={at={(0.5 ,-0.20)},
anchor=north,legend  columns =-1},
ylabel ={Memory Usage (KB)},
xlabel ={Transmissions},
symbolic x coords ={10,100,250},
xtick=data,
nodes  near  coords ,
nodes  near  coords  align ={vertical},
]
\addplot  coordinates  {(10,25.4) (100,25.4) (250,25.4)};
\addplot  coordinates  {(10,25.4) (100,25.4) (250,25.4)};
\legend{10KB,20KB}
\end{axis}
\end{tikzpicture}

我的图表是这样的：

Answer 1

\documentclass[border = 5pt]{standalone}

\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
  \begin{axis}[
    ymin = 0, ymax = 28,
    ybar,
    enlarge x limits=0.3,
    legend  style={at={(0.5 ,-0.20)},
    anchor=north,legend  columns =-1},
    ylabel ={Memory Usage (KB)},
    xlabel ={Transmissions},
    symbolic x coords ={10,100,250},
    xtick=data,    
    nodes  near  coords  align ={vertical},
  ]

  \addlegendimage{empty legend}
  \addplot[nodes  near  coords, fill = blue!30]  coordinates  {(10,25.4) (100,25.4) (250,25.4)};
  \addplot  coordinates  {(10,25.4) (100,25.4) (250,25.4)};

  \addlegendentry{Data Size}
  \addlegendentry{100KB}
  \addlegendentry{20KB}
  %\legend{10KB,20KB}
  \end{axis}
\end{tikzpicture}
\end{document}

1. 消除nodes near coords

2. 使用\addlegendentry{Data Size}

3. 设置限制ymax

Answer 2

这只是对 caverac 的精彩回答的一个小补充，展示了如何将两者合并nodes near coords为一。

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\newcounter{mynodeindex}
\pgfplotsset{%based on https://tex.stackexchange.com/a/75811/121799
    step nodeindex/.code={\stepcounter{mynodeindex}},
    name nodes near coords/.style={
        every node near coord/.append style={/pgfplots/step nodeindex,
            name=#1-\themynodeindex,
            alias=#1-last,
        },
    },
    name nodes near coords/.default=coordnode
}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
ybar,
enlargelimits=0.3,
legend  style={at={(0.5 ,-0.20)},
anchor=north,legend  columns =-1},
ylabel ={Memory Usage (KB)},
xlabel ={Transmissions},
symbolic x coords ={10,100,250},
xtick=data,
nodes  near  coords={},
nodes  near  coords  align ={vertical},
name nodes near coords
]
\addplot  coordinates  {(10,28) (100,28) (250,28)};
\addplot  coordinates  {(10,28) (100,28) (250,28)};
\legend{10KB,20KB}
\end{axis}
\pgfmathtruncatemacro{\Xmax}{\themynodeindex/2}
\foreach \X [evaluate=\X as \Y using {int(\X+\Xmax)}]  in {1,...,\Xmax}
{\path (coordnode-\X) -- (coordnode-\Y) node[midway,yshift=2pt] {28};}
\end{tikzpicture}
\end{document}