color coding using scalar mappable in matplotlib

问题

is a subplot I created using matplotlib. Is it possible to code the colors on the basis of a pre-defined range? I want to pass an additional parameter, voltage to the function drawLoadDuration and define a scale (using if-else construct?) that sets the color. Higher the voltage, darker the shade. Also, for some reason, the y-tick labels for the colorbar are not showing. Any lead is most welcome...Thanks!

import matplotlib.cm
from pylab import *
import numpy as np

f, (ax1, ax2, ax3) = plt.subplots(3, sharex=True, sharey=False)

#other subplots

ax3.set_title('Load Profile')
ax3.patch.set_facecolor('silver')
ax3.grid(True)

cmap= plt.cm.bone_r   
barHeight = 3
ticklist = []
def drawLoadDuration(period, starty, opacity):
    ax3.broken_barh((period), (starty, barHeight), alpha=opacity, facecolors=cmap(opacity), lw=0.5, zorder=2)
    ticklist.append(starty+barHeight/2.0)
    return 0

drawLoadDuration([(0, 5), (13, 4), (19, 3), (23, 1)], 3, 0.5)   #Fan
drawLoadDuration([(19, 1)], 9, 0.65)    #Tube Light
drawLoadDuration([(19, 5)], 15, 0.35)   #Bulb
drawLoadDuration([(7, 2), (16, 1)], 21, 0.28)   #Charger
drawLoadDuration([(15, 0.5), (20, 1)], 27, 0.7) #Television
drawLoadDuration([(9, 1), (17, 1)], 33, 1)  #Pump
drawLoadDuration([(2,4)], 39, 0.8)    #Scooter

ax3.set_ylim(0, 45)
ax3.set_xlim(0, 24)
ax3.set_xlabel('Time (Hours)')
ax3.set_yticks(ticklist)

xticklist = np.linspace(0.5, 24, 48)
ax3.set_xticks(xticklist)

ax3.set_xticklabels(["{}{}m".format(int(h%12+12*(h%12==0)),
                     {0:"p",1:"a"}[(h%24)<12]) if ((h*10)%10)==0 \
                    else "" for h in xticklist], fontsize='9', rotation=90)

ax3.tick_params('x', colors=cmap(1.0), tick1On=True)
ax3.set_yticklabels(['Fan', 'Tube light', 'Bulb', 'Cellphone Charger', 'Television', 'Pump', 'Scooter'])

######################### Code Block for Colorbar
sm = matplotlib.cm.ScalarMappable(cmap=cmap)    # create a scalarmappable from the colormap
sm.set_array([])

cbar = f.colorbar(sm, ticks=[-3, -2, -1, 0, 1, 2, 3], aspect=10, orientation='vertical', ax=ax3)  # using scalarmappable to create colorbar

cbar.ax.text(3, 0.65, 'Power', rotation=90)
cbar.ax.set_yticklabels(['>1000', '>800', '>500', '>200', '>100', '<10'])       #not working!!!

plt.show()

回答1:

You may create a normalization instance, matplotlib.colors.Normalize(vmin=0, vmax=1000) as to map the voltage values to the range between 0 and 1, which will then be understood by the colormap. Inside the plotting function you would use this normalization as facecolors=cmap(norm(voltage)).

import matplotlib.cm
import matplotlib.pyplot as plt
import numpy as np

f, ax3 = plt.subplots()

ax3.set_title('Load Profile')
ax3.patch.set_facecolor('silver')
ax3.grid(True)

cmap= plt.cm.bone_r
# create normalization instance
norm = matplotlib.colors.Normalize(vmin=0, vmax=1000) 
# create a scalarmappable from the colormap
sm = matplotlib.cm.ScalarMappable(cmap=cmap, norm=norm)    
sm.set_array([])  
barHeight = 3
ticklist = []
def drawLoadDuration(period, starty, voltage):
    ax3.broken_barh((period), (starty, barHeight), alpha=1, 
                    facecolors=cmap(norm(voltage)), lw=0.5, zorder=2)
    ticklist.append(starty+barHeight/2.0)
    return 0

drawLoadDuration([(0, 5), (13, 4), (19, 3), (23, 1)], 3, 500)   #Fan
drawLoadDuration([(19, 1)], 9, 650)    #Tube Light
drawLoadDuration([(19, 5)], 15, 350)   #Bulb
drawLoadDuration([(7, 2), (16, 1)], 21, 280)   #Charger
drawLoadDuration([(15, 0.5), (20, 1)], 27, 700) #Television
drawLoadDuration([(9, 1), (17, 1)], 33, 1000)  #Pump
drawLoadDuration([(2,4)], 39, 800)    #Scooter

ax3.set_ylim(0, 45)
ax3.set_xlim(0, 24)
ax3.set_xlabel('Time (Hours)')
ax3.set_yticks(ticklist)

xticklist = np.linspace(0.5, 24, 48)
ax3.set_xticks(xticklist)

ax3.set_xticklabels(["{}{}m".format(int(h%12+12*(h%12==0)),
                     {0:"p",1:"a"}[(h%24)<12]) if ((h*10)%10)==0 \
                    else "" for h in xticklist], fontsize='9', rotation=90)

ax3.tick_params('x', colors=cmap(1.0), tick1On=True)
ax3.set_yticklabels(['Fan', 'Tube light', 'Bulb', 'Cellphone Charger', 'Television', 'Pump', 'Scooter'])

######################### Code Block for Colorbar
# using scalarmappable to create colorbar
cbar = f.colorbar(sm, ticks=[10,100,200,500,800,1000], aspect=10, orientation='vertical', ax=ax3, label='Power')  

plt.show()

来源：https://stackoverflow.com/questions/43442925/color-coding-using-scalar-mappable-in-matplotlib