我想要得到两个图，使得每个点都有到 x 轴的垂直线（在一个图上），并且每个点都有到 y 轴的垂直线（在另一个图上）。像这样：
以下是我目前所掌握的信息：
\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepgfplotslibrary{groupplots}
\newcommand{\datapthreeone}{prob3.dat}
\begin{filecontents*}{\datapthreeone}
x1 y1 averX averY Ex Ey
2.000, 3.000, -0.714, 1.000, 1.000, -0.714
1.000, 2.000, -1.714, 0.000, 0.000, -1.714
1.000, 1.000, -1.714, -1.000, -1.000, -1.714
2.000, 2.000, -0.714, 0.000, 0.000, -0.714
4.000, 2.000, 1.286, 0.000, 0.000, 1.286
4.000, 3.000, 1.286, 1.000, 1.000, 1.286
5.000, 1.000, 2.286, -1.000, -1.000, 2.286
\end{filecontents*}
\begin{document}
\begin{figure}
\begin{center}
\begin{tikzpicture}
\begin{groupplot}[group style={group size=2 by 2, horizontal sep=4em, vertical sep=5em}]
\nextgroupplot[xmin=-2, xmax=2, ymin=-2.5, ymax=2.5, legend style={font=\fontsize{7}{9}\selectfont}, title = (c) PCA Projection Points]
\addplot [only marks, line width = 0.3mm, mark=x, blue, mark options={scale=1.2}]table[x index=4, y index=5, only marks,col sep=comma] {\datapthreeone}; \addlegendentry{\emph{Projected Data}}
\addplot [-latex, dashed, blue, domain=-2:2, samples=2]{0*x + 0};
\addplot[-latex, dashed]coordinates {(-3,0) (2.5,0)};
\addplot[-latex, dashed]coordinates {(0,-2.5) (0,2.5)};
\nextgroupplot[xmin=-2, xmax=2, ymin=-2.5, ymax=2.5, legend style={font=\fontsize{7}{9}\selectfont}, title = (c) PCA Projection Points]
\addplot [only marks, line width = 0.3mm, mark=x, blue, mark options={scale=1.2}]table[x index=4, y index=5, only marks,col sep=comma] {\datapthreeone}; \addlegendentry{\emph{Projected Data}}
\addplot [-latex, dashed, blue, domain=-2:2, samples=2]{0*x + 0};
\addplot[-latex, dashed]coordinates {(-3,0) (2.5,0)};
\addplot[-latex, dashed]coordinates {(0,-2.5) (0,2.5)};
\end{groupplot}
\end{tikzpicture}
\end{center}
\end{figure}
\end{document}
答案1
这是我在 pgfplots 手册中发现的（http://pgfplots.sourceforge.net/pgfplots.pdf)：
您需要在命令中添加ycomb或选项，在这种情况下，它会水平或垂直连接坐标。当然，还有一种更聪明的方法来编写直角代码……xcomb\addplot [..] ...
\documentclass{article}
\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
\pgfplotsset{compat=newest,legend style={font=\fontsize{7}{9}\selectfont}}
\usepackage{graphicx}
\newcommand{\datapthreeone}{prob3.dat}
\begin{filecontents*}{\datapthreeone}
x1 y1 averX averY Ex Ey
2.000, 3.000, -0.714, 1.000, 1.000, -0.714
1.000, 2.000, -1.714, 0.000, 0.000, -1.714
1.000, 1.000, -1.714, -1.000, -1.000, -1.714
2.000, 2.000, -0.714, 0.000, 0.000, -0.714
4.000, 2.000, 1.286, 0.000, 0.000, 1.286
4.000, 3.000, 1.286, 1.000, 1.000, 1.286
5.000, 1.000, 2.286, -1.000, -1.000, 2.286
\end{filecontents*}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
title= (c) PCA Projection Points,
xmin = -2, xmax =2,ymin=-2.5, ymax=2.5]
\addplot [only marks, line width = 0.3mm, mark=x, blue, mark options={scale=1.2}]table[x index=4, y index=5, only marks,col sep=comma] {\datapthreeone}; \addlegendentry{\emph{Projected Data}}
\addplot[ycomb, red] table[x index=4, y index=5,col sep=comma] {\datapthreeone};
\addplot [-latex, dashed, blue, domain=-2:2, samples=2]{0*x + 0};
\addplot[-latex, dashed]coordinates {(-3,0) (2.5,0)};
\addplot[-latex, dashed]coordinates {(0,-2.5) (0,2.5)};
\draw[red] (0.9,0) -- (0.9,0.2) -- (1,0.2);
\draw[red] (-0.1,0) -- (-0.1,0.2) -- (0,0.2);
\draw[red] (-1.1,0) -- (-1.1,0.2) -- (-1,0.2);
\draw[red] (-0.9,0) -- (-0.9,-0.2) -- (-1,-0.2);
\draw[red] (1.1,0) -- (1.1,-0.2) -- (1,-0.2);
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}
\begin{axis}[
title= (c) PCA Projection Points,
xmin = -2, xmax =2,ymin=-2.5, ymax=2.5]
\addplot [only marks, line width = 0.3mm, mark=x, blue, mark options={scale=1.2}]table[x index=4, y index=5, only marks,col sep=comma] {\datapthreeone}; \addlegendentry{\emph{Projected Data}}
\addplot[xcomb, red] table[x index=4, y index=5,col sep=comma] {\datapthreeone};
\addplot [-latex, dashed, blue, domain=-2:2, samples=2]{0*x + 0};
\addplot[-latex, dashed]coordinates {(-3,0) (2.5,0)};
\addplot[-latex, dashed]coordinates {(0,-2.5) (0,2.5)};
\end{axis}
\end{tikzpicture}
\end{document}
