Python中的 Matplotlib.pyplot.csd()
Matplotlib是Python中的一个库,它是 NumPy 库的数值数学扩展。 Pyplot是Matplotlib模块的基于状态的接口,它提供了一个类似 MATLAB 的接口。
matplotlib.pyplot.csd()函数
matplotlib 库的 pyplot 模块中的csd()函数用于绘制交叉光谱密度。
Syntax: matplotlib.pyplot.csd(x, y, NFFT=None, Fs=None, Fc=None, detrend=None, window=None, noverlap=None, pad_to=None, sides=None, scale_by_freq=None, return_line=None, \*, data=None, \*\*kwargs)
Parameters: This method accept the following parameters that are described below:
- x, y: These parameter are the sequence of data.
- Fs : This parameter is a scalar. Its default value is 2.
- window: This parameter take a data segment as an argument and return the windowed version of the segment. Its default value is window_hanning()
- sides: This parameter specifies which sides of the spectrum to return. This can have following values : ‘default’, ‘onesided’ and ‘twosided’.
- pad_to : This parameter contains the integer value to which the data segment is padded.
- NFFT : This parameter contains the number of data points used in each block for the FFT.
- detrend : This parameter contains the function applied to each segment before fft-ing, designed to remove the mean or linear trend {‘none’, ‘mean’, ‘linear’}.
- scale_by_freq : This parameter is allows for integration over the returned frequency values.
- noverlap : This parameter is the number of points of overlap between blocks.
- Fc : This parameter is the center frequency of x.
- return_line : This parameter include the line object plotted in the returned values.
Returns: This returns the following:
- Pxy:This returns the values for the cross spectrum P_{xy} before scaling.
- freqs :This returns the frequencies for the elements in Pxy.
- line :This returns the line created by this function.
The resultant is (Pxy, freqs, line)
下面的示例说明了 matplotlib.pyplot 中的 matplotlib.pyplot.csd()函数:
示例 #1:
# Implementation of matplotlib function
import numpy as np
import matplotlib.pyplot as plt
dt = 0.01
t = np.arange(0, 30, dt)
nse1 = np.random.randn(len(t))
nse2 = np.random.randn(len(t))
s1 = 1.5 * np.sin(2 * np.pi * 10 * t) + nse1
s2 = np.cos(np.pi * t) + nse2
plt.csd(s1, s2**2, 128, 1./dt)
plt.xlabel('Frequency')
plt.ylabel('CSD(db)')
plt.title('matplotlib.pyplot.csd() function Example',
fontweight ="bold")
plt.show()
输出:
示例 #2:
#Implementation of matplotlib function
import numpy as np
import matplotlib.pyplot as plt
dt = 0.01
t = np.arange(0, 30, dt)
nse1 = np.random.randn(len(t))
nse2 = np.random.randn(len(t))
r = np.exp(-t/0.05)
cnse1 = np.convolve(nse1, r, mode='same')*dt
cnse2 = np.convolve(nse2, r, mode='same')*dt
s1 = 1.5 * np.sin(2*np.pi*10*t) + cnse1
s2 = np.cos(np.pi*t) + cnse2 + np.sin(2*np.pi*10*t)
plt.plot(t, s1, t, s2)
plt.xlim(0, 5)
plt.ylabel('s1 and s2')
plt.grid(True)
plt.show()
plt.csd(s1, s2, 256, 1./dt)
plt.ylabel('CSD(db)')
plt.xlabel('Frequency')
plt.title('matplotlib.pyplot.csd() function Example'
,fontweight="bold")
plt.show()
输出: