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dsp.Histogram System object

Histogram of input or sequence of inputs

Description

The Histogram object generates a histogram for an input or a sequence of inputs.

To generate a histogram for an input or a sequence of inputs:

  1. Create the dsp.Histogram object and set its properties.

  2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects? (MATLAB).

Creation

Syntax

hist = dsp.Histogram
hist = dsp.Histogram(min,max,numbins)
hist = dsp.Histogram(Name,Value)

Description

hist = dsp.Histogram returns a histogram object, hist, that computes the frequency distribution of the elements in each input matrix.

example

hist = dsp.Histogram(min,max,numbins) returns a histogram object, hist, with the LowerLimit property set to min, UpperLimit property set to max, and NumBins property set to numbins.

hist = dsp.Histogram(Name,Value) returns a histogram object, hist, with each specified property set to the specified value. Enclose each property name in single quotes. Unspecified properties have default values.

Properties

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Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects (MATLAB).

Specify the lower boundary of the lowest-valued bin as a real-valued scalar. NaN and Inf are not valid values for this property.

Tunable: Yes

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

Specify the upper boundary of the highest-valued bin as a real-valued scalar. NaN and Inf are not valid values for this property.

Tunable: Yes

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

Specify the number of bins in the histogram.

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

Specify how the histogram calculation is performed over the data as All or Column.

Specify whether the histogram object normalizes the output vector, v, so that sum(v)=1. When you set this property to true, the output vector is normalized. When you set it to false, the object supports fixed-point operations and does not use this property for normalization.

Set this property to true to enable running histogram calculations for the input elements over successive calls to the algorithm. Set this property to false to compute a histogram for the current input.

Set this property to true to enable resetting the running histogram. When you set the property to true, specify a reset input to the object algorithm that resets the running histogram. When this property is false, the histogram object does not reset.

Dependencies

This property applies when you set the RunningHistogram property to true.

Specify the event that resets the running histogram as Rising edge, Falling edge, Either edge, or Non-zero.

Dependencies

This property applies when you set the ResetInputPort property to true.

Fixed-Point Properties

Specify the rounding method.

Specify the overflow action as Wrap or Saturate.

Specify the product fixed-point data type as Same as input or Custom.

Specify the product fixed-point type as a scaled numerictype object with a Signedness of Auto.

Dependencies

This property applies when you set the ProductDataType property to Custom.

Specify the accumulator fixed-point data type as one of Same as product, Same as input, or Custom |.

Specify the accumulator fixed-point type as a scaled numerictype object with a Signedness of Auto.

Dependencies

This property applies when you set the AccumulatorDataType property to Custom.

Usage

For versions earlier than R2016b, use the step function to run the System object™ algorithm. The arguments to step are the object you created, followed by the arguments shown in this section.

For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Syntax

y = hist(x)
y = hist(x,r)

Description

example

y = hist(x) returns a histogram y for the input data x . When the RunningHistogram property is true, y corresponds to the histogram of the input elements over successive calls to the algorithm.

y = hist(x,r) resets the histogram state based on the reset signal, r and the object's ResetCondition property. You can reset the histogram state only when the RunningHistogram and the ResetInputPort properties are true.

Input Arguments

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Data input, specified as a vector, matrix, or N-D array. If x is a matrix, each column is treated as an independent channel.

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

Reset signal, specified as a scalar. The reset signal resets the histogram state based on the value of r and the object's ResetCondition property.

Dependencies

You can reset the histogram state only when the RunningHistogram and the ResetInputPort properties are true.

Data Types: single | double | int8 | int16 | int32 | logical

Output Arguments

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Histogram output of the input signal, returned as a scalar, vector, or matrix. The output depends on the setting of Dimension:

  • 'Column' –– The object computes the histogram value of each input channel. If the input is a column vector, the output is a scalar. If the input is a multichannel signal, the output signal is 1-by-N vector, where N is the number of input channels.

  • 'All' –– The object computes the histogram value over all input channels.

Data Types: single | double | uint32

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

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stepRun System object algorithm
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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Note: If you are using R2016a or an earlier release, replace each call to the object with the equivalent step syntax. For example, obj(x) becomes step(obj,x).

Compute a histogram with four bins, for possible input values 1 through 4.

hist = dsp.Histogram(1,4,4);
y = hist([1 2 2 3 3 3 4 4 4 4]')
y = 4×1

     1
     2
     3
     4

Algorithms

This object implements the algorithm, inputs, and outputs described on the Histogram block reference page. The object properties correspond to the block parameters, except:

  • The Reset port block parameter corresponds to both the ResetCondition and the ResetInputPort object properties.

  • The Find histogram over block parameter corresponds to the Dimension property of the object.

Extended Capabilities

See Also

System Objects

Introduced in R2012a