PGFPlots 常数 x 处的线图

Question

在这和这问题，我们学习了如何通过提供samples y=1（samples y=0似乎也有效）或y domain=0:0摆脱网格/矩阵在 PGFPlots 中绘制 3D 轴中的实线图。

但是，当我们尝试在 XY 平面（其中x=const.，而不是X-Z-平面（其中y=const.））绘制线图时，我无法让它在“垂直”方向上工作。结果不是线图，而是“假”3D 图，颜色图仍然完好无损：

%!TEX TS-program = lualatex
\documentclass{article}

\usepackage{pgfplots}
    \pgfplotsset{compat=newest}

\begin{document}
    \begin{tikzpicture}
        \begin{axis}[
            xlabel={x},
            ylabel={y},
            zlabel={z},
            domain=0:5*360,
            y domain=0:5*360,
            surf
            ]
            % These work:
            \addplot3[ultra thick, samples y=1] ({x}, {0}, {cos(x)});
            \addplot3[ultra thick, samples y=1] ({x}, {0}, {cos(x)+4});

            % This is in analogy to above, but does not work
            % (Package pgfplots Warning: the current plot has no coordinates (or all have been filtered away)). 
            \addplot3[ultra thick, samples=1] ({5*360}, {y}, {cos(y)+2});

            % These work, but don't give a line plot:
            \addplot3[ultra thick, domain=5*360:5*360] ({x}, {y}, {cos(y)+2});
            \addplot3[ultra thick] ({5*360}, {y}, {cos(y)+2});
        \end{axis}
    \end{tikzpicture}
\end{document}

得到：

我不知道为什么\addplot3[ultra thick, samples=1] ({5*360}, {y}, {cos(y)+2});不起作用。我们如何才能在第二个方向上生成实线图？

Answer 1

这有点类似于您自己的答案，但可以说是从不同的角度。您正在考虑参数图，其中x和y只是参数或占位符，不要与x和y坐标混淆。为了使这一点更清楚一点，我将参数重命名为t。实际上，这实际上与您的答案相同（surf删除了并使图变得平滑）。我还添加了一个不沿任何轴的图来重申这一点。

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}

\begin{document}
    \begin{tikzpicture}
        \begin{axis}[
            xlabel={$x$},
            ylabel={$y$},
            zlabel={$z$},
            domain=0:5*360,
            y domain=0:5*360,
            samples=101,smooth
            ]
            % These work:
            \addplot3[ultra thick,variable=\t, samples y=0] ({t}, {0}, {cos(t)});
            \addplot3[ultra thick,variable=\t, samples y=0] ({t}, {0}, {cos(t)+4});
            \addplot3[ultra thick,variable=\t, samples y=0] ({5*360}, {t}, {cos(t)+2});
            \addplot3[ultra thick,variable=\t, samples y=0,color=blue] 
            ({900+800*cos(t)}, {900+800*sin(t)}, {cos(12*t)+1});
        \end{axis}
    \end{tikzpicture}
\end{document}

Answer 2

如果我们交换参数函数，我们可以依赖y samples=0如下工作方法：

%!TEX TS-program = lualatex
\documentclass{article}

\usepackage{pgfplots}
    \pgfplotsset{compat=newest}

\begin{document}
    \begin{tikzpicture}
        \begin{axis}[
            xlabel={x},
            ylabel={y},
            zlabel={z},
            domain=0:5*360,
            y domain=0:5*360,
            surf
            ]
            % These work:
            \addplot3[ultra thick, samples y=1] ({x}, {0}, {cos(x)});
            \addplot3[ultra thick, samples y=1] ({x}, {0}, {cos(x)+4});

            % Swapping around the parametric functions allows it to work:
            \addplot3[ultra thick, samples y=1] ({5*360}, {x}, {cos(x)+2});
        \end{axis}
    \end{tikzpicture}
\end{document}

得到：