调用signal.firwin时在Python函数中获取值错误

I am using Least Square filter function in python which is firwin and it is in signal library and when i am calling the function it is raising Value Error.

我在python中使用最小二乘滤波器函数,它是firwin,它在信号库中,当我调用函数时,它会引发Value Error。

My Code Snippet:

我的代码片段:

Fs = 100

epochs = n/Fs

nyquist = Fs/2

lower_filter_bound = 7;

upper_filter_bound = 13;

transition_width = 0.7;

filter_order = np.round((Fs/lower_filter_bound))

idealresponse = [ 0, 0, 1, 1, 0, 0 ];

filterName = 'Band pass filtered';

F = [0, (((1-transition_width)*lower_filter_bound)/nyquist), 
(lower_filter_bound/nyquist),(upper_filter_bound/nyquist),(((1+transition_width)*upper_filter_bound)/nyquist), nyquist/nyquist];

filterweights = sig.firwin(filter_order, F, idealresponse)

Error:

Traceback (most recent call last):
  File "File.py", line 34, in <module>
    filterweights = sig.firwin(filter_order, F, idealresponse)

raise ValueError("Invalid cutoff frequency: frequencies must be "
ValueError: Invalid cutoff frequency: frequencies must be greater than 0 and less than nyq.

1 个解决方案

#1

The least squares FIR filter design function in scipy is scipy.signal.firls (not scipy.signal.firwin).

scipy中的最小二乘FIR滤波器设计函数是scipy.signal.firls(不是scipy.signal.firwin)。

firls requires an odd number of taps, so you'll have to ensure that filter_order is odd.

firls需要奇数个抽头,所以你必须确保filter_order是奇数。

If firwin is actually the function that you meant to use, then take another look at the docstring. In particular:

如果firwin实际上是您打算使用的函数,那么再看一下docstring。特别是:

firwin does not take an argument for the ideal response. It is only given the band edges in the cutoff argument.

firwin没有对理想的反应进行论证。它只在cutoff参数中给出了波段边缘。

The description of the cutoff argument specifically says this argument must not contain 0 and the Nyquist frequency.

截止参数的描述明确说明该参数不得包含0和奈奎斯特频率。

You appear to be creating a bandpass filter. There is an example of this in the docstring:

您似乎正在创建带通滤波器。在docstring中有一个这样的例子:
```
Band-pass:

>>> f1, f2 = 0.1, 0.2
>>> signal.firwin(numtaps, [f1, f2], pass_zero=False)
array([ 0.06301614,  0.88770441,  0.06301614])
```
The first argument of firwin must be an integer, not a float.

firwin的第一个参数必须是整数,而不是浮点数。

Here's how you implement your filter using firwin:

以下是使用firwin实现过滤器的方法:

lower = lower_filter_bound/nyquist
upper = upper_filter_bound/nyquist
filterweights = sig.firwin(int(filter_order), [lower, upper], pass_zero=False)

If you need more flexibility in the design of your FIR filter, take a look at scipy.signal.firwin2.

如果您需要更灵活地设计FIR滤波器,请查看scipy.signal.firwin2。

#1