scipy.signal.upfirdn¶
- scipy.signal.upfirdn(h, x, up=1, down=1, axis=- 1, mode='constant', cval=0)[source]¶
Upsample, FIR filter, and downsample.
- Parameters
- harray_like
1-D FIR (finite-impulse response) filter coefficients.
- xarray_like
Input signal array.
- upint, optional
Upsampling rate. Default is 1.
- downint, optional
Downsampling rate. Default is 1.
- axisint, optional
The axis of the input data array along which to apply the linear filter. The filter is applied to each subarray along this axis. Default is -1.
- modestr, optional
The signal extension mode to use. The set
{"constant", "symmetric", "reflect", "edge", "wrap"}correspond to modes provided bynumpy.pad."smooth"implements a smooth extension by extending based on the slope of the last 2 points at each end of the array."antireflect"and"antisymmetric"are anti-symmetric versions of"reflect"and"symmetric". The mode “line” extends the signal based on a linear trend defined by the first and last points along theaxis.New in version 1.4.0.
- cvalfloat, optional
The constant value to use when
mode == "constant".New in version 1.4.0.
- Returns
- yndarray
The output signal array. Dimensions will be the same as x except for along axis, which will change size according to the h, up, and down parameters.
Notes
The algorithm is an implementation of the block diagram shown on page 129 of the Vaidyanathan text [1] (Figure 4.3-8d).
The direct approach of upsampling by factor of P with zero insertion, FIR filtering of length
N, and downsampling by factor of Q is O(N*Q) per output sample. The polyphase implementation used here is O(N/P).New in version 0.18.
References
- 1
P. P. Vaidyanathan, Multirate Systems and Filter Banks, Prentice Hall, 1993.
Examples
Simple operations:
>>> from scipy.signal import upfirdn >>> upfirdn([1, 1, 1], [1, 1, 1]) # FIR filter array([ 1., 2., 3., 2., 1.]) >>> upfirdn([1], [1, 2, 3], 3) # upsampling with zeros insertion array([ 1., 0., 0., 2., 0., 0., 3., 0., 0.]) >>> upfirdn([1, 1, 1], [1, 2, 3], 3) # upsampling with sample-and-hold array([ 1., 1., 1., 2., 2., 2., 3., 3., 3.]) >>> upfirdn([.5, 1, .5], [1, 1, 1], 2) # linear interpolation array([ 0.5, 1. , 1. , 1. , 1. , 1. , 0.5, 0. ]) >>> upfirdn([1], np.arange(10), 1, 3) # decimation by 3 array([ 0., 3., 6., 9.]) >>> upfirdn([.5, 1, .5], np.arange(10), 2, 3) # linear interp, rate 2/3 array([ 0. , 1. , 2.5, 4. , 5.5, 7. , 8.5, 0. ])
Apply a single filter to multiple signals:
>>> x = np.reshape(np.arange(8), (4, 2)) >>> x array([[0, 1], [2, 3], [4, 5], [6, 7]])
Apply along the last dimension of
x:>>> h = [1, 1] >>> upfirdn(h, x, 2) array([[ 0., 0., 1., 1.], [ 2., 2., 3., 3.], [ 4., 4., 5., 5.], [ 6., 6., 7., 7.]])
Apply along the 0th dimension of
x:>>> upfirdn(h, x, 2, axis=0) array([[ 0., 1.], [ 0., 1.], [ 2., 3.], [ 2., 3.], [ 4., 5.], [ 4., 5.], [ 6., 7.], [ 6., 7.]])