在 matplotlib 中创建堆叠柱面图

Question

matplotlib 可以像下面这样绘制一个堆积柱面图吗？如果它只有一根呢？

如果不是，另一种选择是通常的堆叠条形图，条形边缘具有圆角 - 这可能吗？

我搜索了 matplotlib 库和 bar() 文档，但找不到可以做的事情。

Answer 1

我不知道绘制堆叠圆柱条图的直接函数，我认为也没有简单的解决方法。问题是它既不是真正的 2D 也不是 3D。

使用 Matplotlib，您必须使 2D 看起来像 3D。这意味着您必须制作圆柱形状。为了让它看起来不错，你可能还需要一个纹理来呈现阴影的外观。

mplot3d 是 Matplotlib 的 3D 扩展，我用它来制作下面的图。我觉得它看起来有点太 3D。顶部看起来有点扭曲，整个情节是一个角度...... mplot3d 使用起来也有点痛苦。使圆柱体看起来漂亮需要相当多的努力。代码不是很精致，但我确实对其进行了注释。

from __future__ import print_function
from __future__ import division
from __future__ import absolute_import

from mpl_toolkits.mplot3d import Axes3D 

import numpy
import matplotlib 
import matplotlib.pyplot as plt


def plot_cylinder_element(x, z, dz, rx = 5, ry = 5, color = "b"):
    """
    x: left, right
    z: start height
    dz: height of cylinder
    rx, ry = radius of width (x) and depth (y)
    color = color

    Inspired by:
http://matplotlib.1069221.n5.nabble.com/plot-surface-shading-and-clipping-error-td14031.html
    """

    N = 100             # number of elements
    # a lower stride will give more faces. A cylinder with 4 faces is a cube :)
    # I think with N=100 and rstride=2, it will have 50 faces
    # cstride is the height, rstride the circle
    cstride_side = 1000 # only 1 element needed
    rstride_side = 1    # many elements to make a nice cylinder shape
    cstride_top = 10    
    rstride_top = 10

    # parameters of cylinder
    phi = numpy.linspace(0, 2 * numpy.pi, N) 
    _r = numpy.ones(N) 
    _h = numpy.linspace(0, 1, N) 

    # cylinder
    _x = rx * numpy.outer(numpy.cos(phi), _r) + x
    _y = ry * numpy.outer(numpy.sin(phi), _r) 
    _z = dz * numpy.outer(numpy.ones(numpy.size(_r)), _h) + z
    ax.plot_surface(_x, _y, _z, rstride = rstride_side, cstride = cstride_side, linewidth = 0, alpha = 1, color = color) 

    # to cover the gaps between the faces, plot the cylinder again at a slightly smaller radius
    _x *= 0.99
    _y *= 0.99
    ax.plot_surface(_x, _y, _z, rstride = rstride_side + 1, cstride = cstride_side + 1, linewidth=0, alpha=1, color = color) 

    # top
    _x = rx * numpy.outer(numpy.cos(phi), _h) + x
    _y = ry * numpy.outer(numpy.sin(phi), _h) 
    _z = numpy.zeros([N,N]) + z + dz + 0.1
    ax.plot_surface(_x, _y, _z,  rstride = rstride_top, cstride = cstride_top, linewidth = 0, alpha = 1, color = color) 

    # plot again with different stride to mask the gaps    
    ax.plot_surface(_x, _y, _z, rstride = rstride_side + 1, cstride = cstride_side + 1, linewidth=0, alpha=1, color = color) 


def plot_cylinder(x, z, rx = 5, ry = 5):
    """
    x: left-right for each cylinder
    z: list height difference (ie. not cumulative) 
    """
    # list with colors
    colors = ["b", "g", "r", "c", "y", "k"]
    # plot cylinder elements
    _z = 0
    for i in range(len(z)):
        plot_cylinder_element(x, _z, z[i], rx = rx, ry = ry, color = colors[i % len(colors)])  
        _z += z[i]


def cylinder_plot(z, r = 10, dr = 30):
    """
    z: list of different cylinders with for each a list height difference (ie. not cumulative)
    r: radius
    dr: distance between cylinders    
    """
    # different cylinders next to each other
    x = numpy.arange(len(z)) * dr
    # possible difference between width (x) and depth (y)
    rx = r
    ry = r
    # make cylinders
    for i in range(len(z)):
        plot_cylinder(x[i], z[i], rx = rx, ry = ry)


# close earlier plots
plt.close("all")

# make figure
fig = plt.figure() 
ax = Axes3D(fig) 

# set 3D-view
ax.view_init(elev = 10, azim = 280)

# make 3 cylinders, with a different number of elements
cylinder_plot([[5, 10, 5], [3, 5], [1,2,3,4]]) 

# set the labels
ax.set_xlabel('X') 
ax.set_ylabel('Y') 
ax.set_zlabel('Z') 

# show
plt.show()