具有方向的轮廓/曲线 [英] Contour/curve with orientation

问题描述

我将如何绘制一条曲线(也许是在3d模式下)，并用一些东西来显示其前进的方向.例如，显示圆形平面曲线是顺时针方向还是逆时针方向.

How would I plot a curve (in 3d perhaps) with something to show the direction that it's going. For example, to show that a circular plane curve is going clockwise or counterclockwise.

像这里的曲线， http://mathworld.wolfram.com/CauchyIntegralFormula.html

即使现在有一个可比较的功能，我也不确定，因此我没有示例可以向您展示. 感谢您的阅读.

I am not sure even if there is a comparable function right now, so I don't have an example to show you. Thanks for reading.

我对此进行了很多搜索，也不认为您也可以在gnuplot上执行此操作.

I search quite a bit on this, don't think you can do this on gnuplot either.

推荐答案

有趣的问题.除了快速又肮脏的骇客，我没有时间了，所以就此开始(从mpl streamplot中的代码中自由启发)

Interesting question. I have no time for more than a quick and dirty hack, so here we go (liberally inspired from the code in mpl streamplot)

import matplotlib.lines as mlines
import matplotlib.patches as mpatches
import matplotlib.pyplot as plt
import numpy as np

def add_arrow_to_line2D(
    axes, line, arrow_locs=[0.2, 0.4, 0.6, 0.8],
    arrowstyle='-|>', arrowsize=1, transform=None):
    """
    Add arrows to a matplotlib.lines.Line2D at selected locations.

    Parameters:
    -----------
    axes: 
    line: list of 1 Line2D obbject as returned by plot command
    arrow_locs: list of locations where to insert arrows, % of total length
    arrowstyle: style of the arrow
    arrowsize: size of the arrow
    transform: a matplotlib transform instance, default to data coordinates

    Returns:
    --------
    arrows: list of arrows
    """
    if (not(isinstance(line, list)) or not(isinstance(line[0], 
                                           mlines.Line2D))):
        raise ValueError("expected a matplotlib.lines.Line2D object")
    x, y = line[0].get_xdata(), line[0].get_ydata()

    arrow_kw = dict(arrowstyle=arrowstyle, mutation_scale=10 * arrowsize)
    if transform is None:
        transform = axes.transData

    arrows = []
    for loc in arrow_locs:
        s = np.cumsum(np.sqrt(np.diff(x) ** 2 + np.diff(y) ** 2))
        n = np.searchsorted(s, s[-1] * loc)
        arrow_tail = (x[n], y[n])
        arrow_head = (np.mean(x[n:n + 2]), np.mean(y[n:n + 2]))
        p = mpatches.FancyArrowPatch(
            arrow_tail, arrow_head, transform=transform,
            **arrow_kw)
        axes.add_patch(p)
        arrows.append(p)
    return arrows


fig, ax = plt.subplots(1, 1)
t = np.linspace(0., 4*np.pi, 100.)
line = ax.plot(np.log(t+1)*np.cos(t), np.log(t+1)*np.sin(t),"-")
add_arrow_to_line2D(ax, line, arrow_locs=[0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 0.99],
                    arrowsize=1.5)

ax.axis("equal")
ax.set_xlim([-4., 4.])
ax.set_ylim([-4., 4.])
plt.show()

这篇关于具有方向的轮廓/曲线的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！