Documentation 
Discretetime, scalar filter
Refer to dfilt.scalar in Signal Processing Toolbox™ documentation.
dfilt.scalar(g) returns a discretetime, scalar filter object with gain g, where g is a scalar.
Make this filter a fixedpoint or singleprecision filter by changing the value of the Arithmetic property for the filter hd as follows:
To change to singleprecision filtering, enter
set(hd,'arithmetic','single');
To change to fixedpoint filtering, enter
set(hd,'arithmetic','fixed');
For more information about the property Arithmetic, refer to Arithmetic.
dfilt.scalar returns a default, discretetime scalar gain filter object hd, with gain 1.
In this table you see the properties associated with the scalar implementation of dfilt objects.
Note The table lists all the properties that a filter can have. Many of the properties are dynamic, meaning they exist only in response to the settings of other properties. You might not see all of the listed properties all the time. To view all the properties for a filter at any time, use get(hd) where hd is a filter. 
For further information about the properties of this filter or any dfilt object, refer to FixedPoint Filter Properties.
Property Name  Brief Description 

Arithmetic  Defines the arithmetic the filter uses. Gives you the options double, single, and fixed. In short, this property defines the operating mode for your filter. 
CastBeforeSum  Specifies whether to cast numeric data to the appropriate accumulator format (as shown in the signal flow diagrams) before performing sum operations. 
CoeffAutoScale  Specifies whether the filter automatically chooses the proper fraction length to represent filter coefficients without overflowing. Turning this off by setting the value to false enables you to change the CoeffFracLength property to specify the precision used. 
CoeffFracLength  Set the fraction length the filter uses to interpret coefficients. CoeffFracLength is always available, but it is readonly until you set CoeffAutoScale to false. 
CoeffWordLength  Specifies the word length to apply to filter coefficients. 
FilterStructure  Describes the signal flow for the filter object, including all of the active elements that perform operations during filtering — gains, delays, sums, products, and input/output. 
Gain  Returns the gain for the scalar filter. Scalar filters do not alter the input data except by adding gain. 
InputFracLength  Specifies the fraction length the filter uses to interpret input data. 
InputWordLength  Specifies the word length applied to interpret input data. 
OutputFracLength  Determines how the filter interprets the filter output data. You can change the value of OutputFracLength when you set OutputMode to SpecifyPrecision. 
OutputMode  Sets the mode the filter uses to scale the filtered data for output. You have the following choices:

OutputWordLength  Determines the word length used for the output data. 
OverflowMode  Sets the mode used to respond to overflow conditions in fixedpoint arithmetic. Choose from either saturate (limit the output to the largest positive or negative representable value) or wrap (set overflowing values to the nearest representable value using modular arithmetic). The choice you make affects only the accumulator and output arithmetic. Coefficient and input arithmetic always saturates. Finally, products never overflow — they maintain full precision. 
PersistentMemory  Specifies whether to reset the filter states and memory before each filtering operation. Lets you decide whether your filter retains states from previous filtering runs. False is the default setting. 
RoundMode  Sets the mode the filter uses to quantize numeric values when the values lie between representable values for the data format (word and fraction lengths).
The choice you make affects only the accumulator and output arithmetic. Coefficient and input arithmetic always round. Finally, products never overflow — they maintain full precision. 
Signed  Specifies whether the filter uses signed or unsigned fixedpoint coefficients. Only coefficients reflect this property setting. 
States  This property contains the filter states before, during, and after filter operations. States act as filter memory between filtering runs or sessions. The states use fi objects, with the associated properties from those objects. For details, refer to filtstates in Signal Processing Toolbox documentation or in the Help system. 
Create a directform I filter object hd_filt and a scalar object with a gain of 3 hd_gain and cascade them together.
b = [0.3 0.6 0.3]; a = [1 0 0.2]; hd_filt = dfilt.df1(b,a); hd_gain = dfilt.scalar(3); hd_cascade=cascade(hd_gain,hd_filt); fvtool_handle = fvtool(hd_filt,hd_gain,hd_cascade); legend(fvtool_handle,'IIR Filter (direct form I)',... 'Gain','Cascaded Filter');
To view the stages of the cascaded filter, use
hd.Stage(1)
and
hd.Stage(2)