matplotlib 无法绘制彩色希尔伯特曲线？

Question

我正在尝试绘制彩色 2D Hilbert curve using matplotlib. After getting the x and y coordinates, a plain ax.plot(x,y) gives the correct curve, but if I want to color-code the curve using the technique introduced in this post，它给了我一个空的 canvas（因此未显示）。

奇怪的是，原始答案中显示的随机路径有效。

我的代码如下：

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.collections as mcoll
import matplotlib.path as mpath

def xy2d(n,x,y):
    d=0
    s=n/2
    while s>0:
        rx=(x&s)>0
        ry=(y&s)>0
        d+=s*s*((3*rx)^ry)
        s,x,y,rx,ry=rot(s,x,y,rx,ry)
        s/=2
    return d

def d2xy(n,d):
    t=d
    x=y=0
    s=1
    while s<n:
        rx=1&(t/2)
        ry=1&(t^rx)
        s,x,y,rx,ry=rot(s,x,y,rx,ry)
        x+=s*rx
        y+=s*ry
        t/=4
        s*=2
    return x,y

def rot(n,x,y,rx,ry):
    if ry==0:
        if rx==1:
            x=n-1-x
            y=n-1-y
        x,y=y,x

    return n,x,y,rx,ry

#--------------These are copied from SO--------------
def colorline(
    x, y, z=None, ax=None, cmap=plt.get_cmap('copper'), norm=plt.Normalize(0.0, 1.0),
        linewidth=3, alpha=1.0):
    """
    http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb
    http://matplotlib.org/examples/pylab_examples/multicolored_line.html
    Plot a colored line with coordinates x and y
    Optionally specify colors in the array z
    Optionally specify a colormap, a norm function and a line width
    """

    # Default colors equally spaced on [0,1]:
    if z is None:
        z = np.linspace(0.0, 1.0, len(x))

    # Special case if a single number:
    if not hasattr(z, "__iter__"):  # to check for numerical input -- this is a hack
        z = np.array([z])

    z = np.asarray(z)

    segments = make_segments(x, y)
    lc = mcoll.LineCollection(segments, array=z, cmap=cmap, norm=norm,
                              linewidth=linewidth, alpha=alpha)

    if ax is None:
        ax = plt.gca()
    ax.add_collection(lc)

    return lc

def make_segments(x, y):
    """
    Create list of line segments from x and y coordinates, in the correct format
    for LineCollection: an array of the form numlines x (points per line) x 2 (x
    and y) array
    """

    points = np.array([x, y]).T.reshape(-1, 1, 2)
    segments = np.concatenate([points[:-1], points[1:]], axis=1)
    return segments
#--------------These are copied from SO--------------

if __name__=='__main__':

    xs=[]
    ys=[]
    N=16

    for i in range(N**2-1):
        x,y=d2xy(N,i)
        xs.append(x)
        ys.append(y)

    #-------------------Plot------------------------
    figure=plt.figure(figsize=(12,10),dpi=100)
    cmap=plt.cm.jet
    ax=figure.add_subplot(111)

    path = mpath.Path(np.column_stack([xs, ys]))
    #verts = path.interpolated(steps=1).vertices
    verts=path.vertices
    x, y = verts[:, 0], verts[:, 1]
    z = np.linspace(0, 1, len(xs))
    colorline(x, y, z, ax=ax, cmap=cmap, linewidth=1)

    #ax.plot(x,y) # this works, but with blue line
    plt.show(block=False)

我是不是遗漏了什么明显的东西？

我的设置：

python=2.7.14，在蟒蛇 4.4.10
matplotlib=2.0.2=py27h334a7c2_1，也测试了2.1.2=py27h0e671d2_0
numpy=1.14.1

Answer 1

代码有效，但是两个轴限制都是 (0,1)，因此您放大得太大而看不到绘图。似乎 add_collection 不会自动缩放坐标轴。

解决方法是简单地自己缩放坐标轴：

ax.set_ylim(0,15)
ax.set_xlim(0,15)

# or use plt.xlim() if not using object oriented API

matplotlib 无法绘制彩色希尔伯特曲线？

matplotlib can't plot colored Hilbert curve?

python

matplotlib

hilbert-curve