replaceFilters

Replace existing filters with new filters in Filter Analyzer app

Since R2024a

Syntax

replaceFilters(fa,filt1,...,filtn)

replaceFilters(___,Name=Value)

Description

replaceFilters(fa,filt1,...,filtn) replaces all the filters in the Filter Analyzer app fa with new filters. The number of specified filters must be equal to the total number of filters in the app. If you want to replace only a subset of the filters, use FilterNames to specify which ones.

replaceFilters(___,Name=Value) specifies additional options using name-value arguments.

Examples

Replace Existing Filters

Start the Filter Analyzer app with one lowpass filter.

d1 = designfilt("lowpassfir", ...
    PassbandFrequency=0.45,StopbandFrequency=0.55);
fa = filterAnalyzer(d1,FilterNames="LP");

Replace the lowpass filter with a highpass filter.

d2 = designfilt("highpassfir", ...
    PassbandFrequency=0.55,StopbandFrequency=0.45);
replaceFilters(fa,d2,FilterNames="LP")

renameFilters(fa,"LP","HP")

Input Arguments

fa — Filter Analyzer app handle

filterAnalyzer object

Filter Analyzer app handle, specified as a filterAnalyzer object.

filt — Input filter

coefficient matrices | cell array | digitalFilter object

Input filter, specified as coefficient matrices, a cell array, or a digitalFilter object.

For more information, see Import Filter.

Example: b = [1 3 3 1]/6 and a = [3 0 1 0]/3 together specify a third-order lowpass Butterworth filter with a normalized 3-dB frequency of 0.5π rad/sample.

Example: sos2ctf([2 4 2 6 0 2; 3 3 0 6 0 0]) specifies a third-order lowpass Butterworth filter with a normalized 3-dB frequency of 0.5π rad/sample.

Example: d = designfilt("lowpassiir",FilterOrder=3,HalfPowerFrequency=0.5) specifies a third-order lowpass Butterworth filter with a normalized 3-dB frequency of 0.5π rad/sample.

Filter Coefficients

You can use Filter Analyzer to analyze filters specified as numerator and denominator coefficients. If you specify the coefficients as the K-row matrices

$$B=\left[\begin{array}{cccc}{b}_{11}& b_{12}& \cdots & b_{1,m+1}\\ b_{21}& b_{22}& \cdots & b_{2,m+1}\\ ⋮& ⋮& \ddots & ⋮\\ b_{K1}& b_{K2}& \cdots & b_{K,m+1}\end{array}\right],A=\left[\begin{array}{cccc}{a}_{11}& a_{12}& \cdots & a_{1,n+1}\\ a_{21}& a_{22}& \cdots & a_{2,n+1}\\ ⋮& ⋮& \ddots & ⋮\\ a_{K1}& a_{K2}& \cdots & a_{K,n+1}\end{array}\right],$$

Signal Analyzer assumes you have specified the filter as a sequence of K cascaded transfer functions (CTF) such that the full transfer function of the filter is

$$H\left(z\right)=\frac{b_{11}+b_{12}{z}^{-1}+\cdots +b_{1,m+1}{z}^{-m}}{a_{11}+a_{12}{z}^{-1}+\cdots +a_{1,n+1}{z}^{-n}}\times \frac{b_{21}+b_{22}{z}^{-1}+\cdots +b_{2,m+1}{z}^{-m}}{a_{21}+a_{22}{z}^{-1}+\cdots +a_{2,n+1}{z}^{-n}}\times \cdots \times \frac{b_{K1}+b_{K2}{z}^{-1}+\cdots +b_{K,m+1}{z}^{-m}}{a_{K1}+a_{K2}{z}^{-1}+\cdots +a_{K,n+1}{z}^{-n}},$$

where m ≥ 0 is the numerator order of the filter and n ≥ 0 is the denominator order.

• If K = 1, then B and A are row vectors that specify the transfer function of an IIR filter.

• If you specify both B and A as column vectors, Filter Analyzer assumes they represent the transfer function of an IIR filter.

• If B is a scalar, Filter Analyzer assumes you specified the filter as a cascade of all-pole IIR filters with each section having a scaling gain equal to B.

• If A is a scalar, Filter Analyzer assumes you specified the filter as a cascade of FIR filters with each section having a scaling gain equal to 1/A.

Note

• To convert second-order section matrices to cascaded transfer functions, use the sos2ctf function.

• To convert a zero-pole-gain filter representation to cascaded transfer functions, use the zp2ctf function.

Coefficients and Gain

If you have a scaling gain separate from the coefficient values, you can enter it in Filter Analyzer using the Import Filter dialog box. At the command line, you can specify the coefficients and gain as a cell array of the form {B,A,g}, where B and A are as previously defined.

The gain can be a scalar overall gain or a vector of section gains.

• If the gain is a scalar, Filter Analyzer applies the value uniformly to all the cascade filter sections.

• If the gain is a vector, it must have one more element than the number of filter sections in the cascade. Filter Analyzer applies a scale value to each of the filter sections and applies the last value uniformly to all the filter sections.

If you specify the coefficient matrices and gain vector as

$$B=\left[\begin{array}{cccc}{b}_{11}& b_{12}& \cdots & b_{1,m+1}\\ b_{21}& b_{22}& \cdots & b_{2,m+1}\\ ⋮& ⋮& \ddots & ⋮\\ b_{K1}& b_{K2}& \cdots & b_{K,m+1}\end{array}\right],A=\left[\begin{array}{cccc}{a}_{11}& a_{12}& \cdots & a_{1,n+1}\\ a_{21}& a_{22}& \cdots & a_{2,n+1}\\ ⋮& ⋮& \ddots & ⋮\\ a_{K1}& a_{K2}& \cdots & a_{K,n+1}\end{array}\right],g=\left[\begin{array}{ccccc}{g}_1& g_2& \cdots & g_K& g_0\end{array}\right],$$

Signal Analyzer uses the transfer function

$$H\left(z\right)=g_0\left(g_1\frac{b_{11}+b_{12}{z}^{-1}+\cdots +b_{1,m+1}{z}^{-m}}{a_{11}+a_{12}{z}^{-1}+\cdots +a_{1,n+1}{z}^{-n}}\times g_2\frac{b_{21}+b_{22}{z}^{-1}+\cdots +b_{2,m+1}{z}^{-m}}{a_{21}+a_{22}{z}^{-1}+\cdots +a_{2,n+1}{z}^{-n}}\times \cdots \times g_K\frac{b_{K1}+b_{K2}{z}^{-1}+\cdots +b_{K,m+1}{z}^{-m}}{a_{K1}+a_{K2}{z}^{-1}+\cdots +a_{K,n+1}{z}^{-n}}\right).$$

digitalFilter Objects

You can use Filter Analyzer to analyze digitalFilter objects. Use designfilt to generate or edit digital filters based on frequency-response specifications.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | cell
Complex Number Support: Yes

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: FilterNames=["LP" "HP"],SampleRates=[150 3e3]

FilterNames — Names of filters to replace

string vector

Names of filters to replace, specified as a string vector. Filter names are the names that identify the different filters in the app Filters table.

Example: ["LPbutter" "LPelliptic"]

Data Types: char | string

SampleRates — Filter sample rates

1 (default) | scalar | vector

Filter sample rates, specified as a scalar or vector of values specified in Hz.

• If SampleRates is a scalar, the specified value applies to all filters.

• If SampleRates is a vector, it must have a number of elements equal to the number of filters.

This argument does not apply if one or more filters are objects with a sample rate.

Example: [150 3e3]

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Version History

Introduced in R2024a