python如何绘制下三角矩阵的热力图，先看一下效果图

加载必要的包

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns
import scipy.stats as stats 
from matplotlib.ticker import FormatStrFormatter
encoding="utf-8"

加载数据

#读取数据
data = pd.read_excel(