Python打印三维矢量

Question

假设我想取以下三个坐标[x，y，z]：

[0.799319-3.477045e-01 0.490093]

[0.852512 9.113778e-16-0.522708]

[0.296422 9.376042e-01 0.181748]

并将其绘制为向量，向量从原点开始[0,0,0]。我该怎么做呢？我一直在尝试使用matplotlib的箭袋，但我一直得到以下值错误：

ValueError: need at least one array to concatenate

这是我的代码（文档矩阵投影是上面用矩阵表示的三个坐标）：

D1, D2, D3 = zip(*document_matrix_projections)

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.quiver(D1)
plt.show()

Answer 1

函数quiver()需要箭头的位置为X,Y,Z和U,V,W作为箭头的组件。因此，以下脚本可以绘制数据：

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

p0 = [0.799319, -3.477045e-01, 0.490093]
p1 = [0.852512, 9.113778e-16, -0.522708]
p2 = [0.296422, 9.376042e-01, 0.181748]

origin = [0,0,0]
X, Y, Z = zip(origin,origin,origin) 
U, V, W = zip(p0,p1,p2)

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.quiver(X,Y,Z,U,V,W,arrow_length_ratio=0.01)
plt.show()

但结果并不好。如果要使用Mayavi，则以下操作有效：

import numpy as np
import mayavi.mlab as m

p0 = [0.799319, -3.477045e-01, 0.490093]
p1 = [0.852512, 9.113778e-16, -0.522708]
p2 = [0.296422, 9.376042e-01, 0.181748]

origin = [0,0,0]
X, Y, Z = zip(origin,origin,origin) 
U, V, W = zip(p0,p1,p2)

m.quiver3d(X,Y,Z,U,V,W)

Answer 2

使用matplolib的quiver（）的一个不错的替代方法是使用plotly进行绘图，plotly具有交互的优点。以下函数可以使用plotly中的Scatter3d（）绘制矢量。在这里，向量有一个大点来标记方向，而不是箭头。

import numpy as np 
import plotly.graph_objs as go

def vector_plot(tvects,is_vect=True,orig=[0,0,0]):
    """Plot vectors using plotly"""

    if is_vect:
        if not hasattr(orig[0],"__iter__"):
            coords = [[orig,np.sum([orig,v],axis=0)] for v in tvects]
        else:
            coords = [[o,np.sum([o,v],axis=0)] for o,v in zip(orig,tvects)]
    else:
        coords = tvects

    data = []
    for i,c in enumerate(coords):
        X1, Y1, Z1 = zip(c[0])
        X2, Y2, Z2 = zip(c[1])
        vector = go.Scatter3d(x = [X1[0],X2[0]],
                              y = [Y1[0],Y2[0]],
                              z = [Z1[0],Z2[0]],
                              marker = dict(size = [0,5],
                                            color = ['blue'],
                                            line=dict(width=5,
                                                      color='DarkSlateGrey')),
                              name = 'Vector'+str(i+1))
        data.append(vector)

    layout = go.Layout(
             margin = dict(l = 4,
                           r = 4,
                           b = 4,
                           t = 4)
                  )
    fig = go.Figure(data=data,layout=layout)
    fig.show()

绘图可以简单地通过

p0 = [0.799319, -3.477045e-01, 0.490093]
p1 = [0.852512, 9.113778e-16, -0.522708]
p2 = [0.296422, 9.376042e-01, 0.181748]

vector_plot([p0,p1,p2])

上述输出如下：