Question

我尝试使用matplotlib绘制彩色2D Hilbert curve。获得x和y坐标后，普通ax.plot(x,y)会给出正确的曲线，但如果我想使用this post中介绍的技术对曲线进行颜色编码，则给我一个空的画布（没有显示）。

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)

我错过了一些明显的东西吗？

我的设置：

python = 2.7.14，in anaconda 4.4.10
matplotlib = 2.0.2 = py27h334a7c2_1，也经过测试2.1.2 = py27h0e671d2_0
numpy的= 1.14.1

Answer 1

代码正在运行，但是两个轴限制都是(0,1)，因此您放大了以查看绘图。似乎add_collection不会自动缩放轴。

解决方案是自己简单地缩放轴：

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

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

matplotlib不能绘制有色的希尔伯特曲线？

1 个答案: