Python matplotlib：颜色条及其文本标签
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matplotlib: colorbars and its text labels
提问by dimka
I'd like to create a colorbarlegend for a heatmap, such that the labels are in the center of each discrete color. Example borrowed from here:
我想colorbar为 a创建一个图例heatmap，以便标签位于每个离散颜色的中心。从这里借用的示例：
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import ListedColormap
#discrete color scheme
cMap = ListedColormap(['white', 'green', 'blue','red'])
#data
np.random.seed(42)
data = np.random.rand(4, 4)
fig, ax = plt.subplots()
heatmap = ax.pcolor(data, cmap=cMap)
#legend
cbar = plt.colorbar(heatmap)
cbar.ax.set_yticklabels(['0','1','2','>3'])
cbar.set_label('# of contacts', rotation=270)
# put the major ticks at the middle of each cell
ax.set_xticks(np.arange(data.shape[1]) + 0.5, minor=False)
ax.set_yticks(np.arange(data.shape[0]) + 0.5, minor=False)
ax.invert_yaxis()
#labels
column_labels = list('ABCD')
row_labels = list('WXYZ')
ax.set_xticklabels(column_labels, minor=False)
ax.set_yticklabels(row_labels, minor=False)
plt.show()
This generates the following plot:
这将生成以下图：
Ideally I'd like to generate a legend bar which has the four colors and for each color, a label in its center: 0,1,2,>3. How can this be achieved?
理想情况下，我想生成一个图例栏，它具有四种颜色，并且对于每种颜色，其中心都有一个标签：0,1,2,>3。如何做到这一点？
采纳答案by tacaswell
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import ListedColormap
#discrete color scheme
cMap = ListedColormap(['white', 'green', 'blue','red'])
#data
np.random.seed(42)
data = np.random.rand(4, 4)
fig, ax = plt.subplots()
heatmap = ax.pcolor(data, cmap=cMap)
#legend
cbar = plt.colorbar(heatmap)
cbar.ax.get_yaxis().set_ticks([])
for j, lab in enumerate(['import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
fig, ax = plt.subplots()
heatmap = ax.imshow(data)
divider = make_axes_locatable(ax)
cax = divider.append_axes('bottom', size='10%', pad=0.6)
cb = fig.colorbar(heatmap, cax=cax, orientation='horizontal')
cax.set_xlabel('data label') # cax == cb.ax
$','$','$','$>3$']):
cbar.ax.text(.5, (2 * j + 1) / 8.0, lab, ha='center', va='center')
cbar.ax.get_yaxis().labelpad = 15
cbar.ax.set_ylabel('# of contacts', rotation=270)
# put the major ticks at the middle of each cell
ax.set_xticks(np.arange(data.shape[1]) + 0.5, minor=False)
ax.set_yticks(np.arange(data.shape[0]) + 0.5, minor=False)
ax.invert_yaxis()
#labels
column_labels = list('ABCD')
row_labels = list('WXYZ')
ax.set_xticklabels(column_labels, minor=False)
ax.set_yticklabels(row_labels, minor=False)
plt.show()
You were very close. Once you have a reference to the color bar axis, you can do what ever you want to it, including putting text labels in the middle. You might want to play with the formatting to make it more visible.
你非常接近。一旦您有了对颜色条轴的引用，您就可以对其进行任何操作，包括将文本标签放在中间。您可能想要调整格式以使其更明显。
回答by Steven C. Howell
To add to tacaswell's answer, the colorbar()function has an optional caxinput you can use to pass an axis on which the colorbar should be drawn. If you are using that input, you can directly set a label using that axis.
要添加到tacaswell's answer，该colorbar()函数有一个可选cax输入，您可以使用它来传递应在其上绘制颜色条的轴。如果您使用该输入，则可以使用该轴直接设置标签。
