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Vector of SOS filters for cumulative sections


h = cumsec(hd)
h = cumsec(hd,indices)
h = cumsec(hd,indices,secondary)
h = cumsec(hs)
h = cumsec(hs,Name,Value)


h = cumsec(hd) returns a vector h of SOS filter objects with the cumulative sections. Each element in h is a filter with the structure of the original filter. The first element is the first filter section of hd. The second element of h is a filter that represents the combination of the first and second sections of hd. The third element of h is a filter which combines sections 1, 2, and 3 of hd. This pattern continues until the final element of h contains all the sections of hd and should be identical to hd.

h = cumsec(hd,indices) returns a vector h of SOS filter objects whose indices into the original filter are in the vector indices.

h = cumsec(hd,indices,secondary) uses the secondary scaling points secondary in the sections to determine where the sections should be split.

cumsec(hd,...) uses FVTool to plot the magnitude response of the cumulative sections.

h = cumsec(hs) returns the cumulative sections of the dsp.BiquadFilter filter System object™ hs. You can also use the optional input arguments indices and secondary with this syntax. You can also omit the output argument h to use FVTool to plot the magnitude response of the cumulative sections.

h = cumsec(hs,Name,Value) returns the cumulative sections of the filter System object hs with additional options specified by one or more Name,Value pair arguments.

Input Arguments

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Discrete-time dfilt.df1sos, dfilt.df2tsos, dfilt.df2sos, or dfilt.df1tsosfilter object.


dsp.BiquadFilter filter System object.


Filter indices. Use indices to specify the filter sections cumsec uses to compute the cumulative responses.


This option applies only when hd is a df2sos and df1tsos filter. For these second-order section structures, the secondary scaling points refer to the scaling locations between the recursive and the nonrecursive parts of the section (the "middle" of the section). Argument secondary accepts either true or false. By default, secondary is false.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (' '). You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

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For filter System object inputs only, specify the arithmetic used during analysis. When you specify 'double' or 'single', the function performs double- or single-precision analysis. When you specify 'fixed' , the arithmetic changes depending on the setting of the CoefficientDataType property and whether the System object is locked or unlocked.

 Details for Fixed-Point Arithmetic

When you do not specify the arithmetic, the function uses double-precision arithmetic if the filter System object is in an unlocked state. If the System object is locked, the function performs analysis based on the locked input data type.


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This example plots the relative responses of the sections of a sixth-order filter with three sections. Each curve adds one more section to form the filter response.

hs = fdesign.lowpass('n,fc',6,.4); hd = butter(hs);
h = cumsec(hd); hfvt = fvtool(h);
legend(hfvt,'First Section','First Two Sections','Overall  Filter');

See Also


Introduced in R2011a

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