PGF 图箭筒中的中心箭头

Question

我正在尝试让箭筒图与网格完美配合。我希望箭头居中（箭头的中点位于每个单元格的中心，或者箭头的起点位于单元格的中心。

\documentclass{standalone}
\usepackage{pgfplots,}
\pgfplotsset{compat=1.8}

\usepackage{amsmath}

\begin{document}
\def\length{sqrt((2.*x^2-2.2-2.*y^2)^2  + (4.*x^2*y)^2 )}

\begin{tikzpicture}[enter image description here][1]
    \begin{axis}[   enlargelimits = false ,
            view={0}{90},
            domain=-2:2,
            axis equal image
        ]
        \addplot3 [gray,quiver={u={(2.*x^2-2.2-2.*y^2)/\length}, v={4.*x^2*y/\length}, scale arrows=0.2}, -stealth,samples=12] {0};
    \end{axis}

    \begin{scope}%[xshift=4pt,yshift=4pt]
        \draw[step=3.99mm, blue] (0,0) grid (5.5,5.5);
    \end{scope}
\end{tikzpicture}
\end{document}

我不确定“每个箭头”选项是否可行。以下是我目前所得到的

Answer 1

像这样吗？

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.8}

\usepackage{amsmath}

\begin{document}
\def\length{sqrt((2.*x^2-2.2-2.*y^2)^2  + (4.*x^2*y)^2 )}

\begin{tikzpicture}
    \begin{axis}[   enlargelimits = false ,
            view={0}{90},
            domain=-2:2,
            minor x tick num=2, 
            minor y tick num=2,
            axis equal image, grid=both,
            minor grid style={blue,very thin},
            axis equal image
        ]
        \addplot3[white,quiver={u={(2.*x^2-2.2-2.*y^2)/\length}, v={4.*x^2*y/\length}, scale arrows=0.2}, -stealth,samples=12] {0};
        \addplot3[domain=-11/6:11/6,gray,quiver={u={(2.*x^2-2.2-2.*y^2)/\length}, v={4.*x^2*y/\length}, scale arrows=0.2}, -stealth,samples=12] {0};
    \end{axis}

\end{tikzpicture}
\end{document}

解释：除了每行有 13 个方框，每个方框有 12 支箭之外，pgfplots似乎真的将箭移到了边界。在这个提议中，我将箭的范围缩小了 1/12。