isreal(hd) returns 1 if all filter coefficients in filter hd have zero imaginary part. Otherwise, isreal(hd) returns a 0 indicating that the filter is complex. Complex filters have one or more coefficients with nonzero imaginary parts.

Note Quantizing a filter cannot make a real filter into a complex filter.

Examples

To demonstrate the isreal test, this example creates a double-precision filter and fixed-point filter, and tests the coefficients of the fixed-point filter to see if they are strictly real.

d=fdesign.lowpass('n,fp,ap,ast',5,0.4,0.5,20);
hd=design(d,'ellip')

hd =
 
 FilterStructure: 'Direct-Form II, Second-Order Sections'  
      Arithmetic: 'double' 
       sosMatrix: [3x6 double]
ScaleValues: [0.362583368859661;0.918321077151039;
              0.496533475964919;1]
PersistentMemory: false   

% Use d to design the fixed-point filter.
hq=design(d,'ellip');  
% Convert to fixed-point arithmetic.
hq.arithmetic='fixed'; 
isreal(hq)

ans =

     1

isreal - Determine whether filter uses real coefficients

Syntax

Description

Examples

See Also