numpy窗函數

繪制巴特利特窗

巴特利特窗是一種三角形平滑窗

import numpy as np
import matplotlib.pyplot as plt

window = np.bartlett(42)

plt.plot(window)
plt.show()

 

繪制布萊克曼窗

布萊克曼窗形式上是三項余弦值的加和

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.dates import datestr2num

closes = np.loadtxt('AAPL.csv', delimiter=',', usecols=(6,), 
                    converters={1:datestr2num}, unpack=True)
N = 10
window = np.blackman(N)
smoothed = np.convolve(window/window.sum(), closes, mode="same")

plt.plot(smoothed[N:-N], lw=2, label="smoothed")
plt.plot(closes[N:-N], label="closes")
plt.legend(loc="best")
plt.show()

繪制漢明窗

漢明窗是一個加權的余弦函數

hamming函數唯一的參數是輸出點的個數

import numpy as np
import matplotlib.pyplot as plt

window = np.hamming(142)
plt.plot(window)
plt.show()

 

繪制凱澤窗

凱澤窗是以貝塞爾函數定義的

第一個參數為輸出點的個數, 第二個參數為貝塞爾函數中的參數值

import numpy as np
import matplotlib.pyplot as plt

window = np.kaiser(42, 14)
plt.plot(window)
plt.show()

import numpy as np
import matplotlib.pyplot as plt

window = np.kaiser(42, 4)
plt.plot(window)
plt.show()