Update README.md

Signed-off-by: David Rotermund <54365609+davrot@users.noreply.github.com>

numpy/power_mean/README.md

@@ -10,12 +10,46 @@
 
 Questions to [David Rotermund](mailto:davrot@uni-bremen.de)
 
+## The order is important 
+
+You are not allowed to average over the trials before calculating the power. This is the same for calculating the fft power as well as the wavelet power. 
+
+```python
+import numpy as np
+import matplotlib.pyplot as plt
+
+t: np.ndarray = np.linspace(0, 1.0, 10000)
+f: float = 10
+
+sinus_a = np.sin(f * t * 2.0 * np.pi)
+sinus_b = np.sin(f * t * 2.0 * np.pi + np.pi)
+
+plt.plot(t, sinus_a, label="a")
+plt.plot(t, sinus_b, label="b")
+plt.plot(t, (sinus_a + sinus_b) / 2.0, "k--", label="(a+b)/2")
+plt.legend()
+plt.xlabel("t [s]")
+plt.show()
+```
+
+![image0.png]
 
 
 ```python
+import numpy as np
+import matplotlib.pyplot as plt
+
+t: np.ndarray = np.linspace(0, 1.0, 10000)
+f: float = 10
+n: int = 1000
+
+rng = np.random.default_rng(1)
+sinus = np.sin(f * t[:, np.newaxis] * 2.0 * np.pi + 2.0 * np.pi * rng.random((1, n)))
+print(sinus.shape)
+
+plt.plot(t, sinus)
+plt.plot(t, sinus.mean(axis=-1), "k--")
+plt.show()
 ```
 
-
+![image1.png]
-```shell
-```
-