Creating a stacked cylinder bar plot in matplotlib

I don't know of a direct function to plot a stacked cylinder bar plot and I don't think there is an easy workaround either. The problem is that it is neither really 2D or 3D.

With Matplotlib you have to make 2D look like 3D. This means you have to make a cylinder shape. To make it look good you'll probably need a texture as well to give the appearance of shadow.

mplot3d is a 3D extension of Matplotlib and I used it to make the plot below. I think it looks a bit too 3D. The top looks a bit distorted and the whole plot is at an angle... mplot3d is also a bit of a pain to work with. It takes quite some effort to make the cylinder look nice. The code is not very polished, but I did annotate it.

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()