我有一个直方图,可以用下面的MWE复制：
- import pandas as pd
- import matplotlib.pyplot as plt
- import seaborn as sns
- import numpy as np
- pd.Series(np.random.normal(0,100,1000)).plot(kind='hist',bins=50)
这创建了这样的情节：
那么我如何用给定整数的箭头标记bin？
例如,见下文,其中箭头标记包含整数300的bin.
解决方法
您可以使用注释添加箭头：
- import pandas as pd
- import matplotlib.pyplot as plt
- #import seaborn as sns
- import numpy as np
- fig,ax = plt.subplots()
- series = pd.Series(np.random.normal(0,1000))
- series.plot(kind='hist',bins=50,ax=ax)
- ax.annotate("",xy=(300,5),xycoords='data',xytext=(300,20),textcoords='data',arrowprops=dict(arrowstyle="->",connectionstyle="arc3"),)
在这个例子中,我添加了一个从坐标(300,20)到(300,5)的箭头.
为了自动将箭头缩放到bin中的值,您可以使用matplotlib hist绘制直方图并获取值,然后使用numpy在哪里找到哪个bin对应于所需位置.
- import pandas as pd
- import matplotlib.pyplot as plt
- #import seaborn as sns
- import numpy as np
- nbins = 50
- labeled_bin = 200
- fig,ax = plt.subplots()
- series = pd.Series(np.random.normal(0,1000))
- ## plot the histogram and return the bin position and values
- ybins,xbins,_ = ax.hist(series,bins=nbins)
- ## find out in which bin belongs the position where you want the label
- ind_bin = np.where(xbins >= labeled_bin)[0]
- if len(ind_bin) > 0 and ind_bin[0] > 0:
- ## get position and value of the bin
- x_bin = xbins[ind_bin[0]-1]/2. + xbins[ind_bin[0]]/2.
- y_bin = ybins[ind_bin[0]-1]
- ## add the arrow
- ax.annotate("",xy=(x_bin,y_bin + 5),xytext=(x_bin,y_bin + 20),)
- else:
- print "Labeled bin is outside range"