2-D Histogram
Generate histogram of input or sequence of inputs
Library
Statistics
visionstatistics
Description
The 2-D Histogram block computes the frequency distribution
of the elements in the input. You must use the Find the
histogram over parameter to specify whether the block computes
the histogram for Each column of the input
or of the Entire input. The Running
histogram check box allows you to select between basic
operation and running operation, as described below.
The block distributes the elements of the input into the number
of discrete bins specified by the Number of bins parameter, n.
y = hist(u,n) % Equivalent MATLAB code
The 2-D Histogram block sorts all complex input values into bins according to their magnitude.
The histogram value for a given bin represents the frequency of occurrence of the input values bracketed by that bin. You specify the upper boundary of the highest-valued bin in the Upper limit of histogram parameter, BM, and the lower boundary of the lowest-valued bin in the Lower limit of histogram parameter, Bm. The bins have equal width of
and centers located at
Input values that fall on the border between two bins are placed into the lower valued bin; that is, each bin includes its upper boundary. For example, a bin of width 4 centered on the value 5 contains the input value 7, but not the input value 3. Input values greater than the Upper limit of histogram parameter or less than Lower limit of histogram parameter are placed into the highest valued or lowest valued bin, respectively.
The values you enter for the Upper limit of histogram and Lower
limit of histogram parameters must be real-valued scalars. NaN and inf are
not valid values for the Upper limit of histogram and Lower
limit of histogram parameters.
Basic Operation
When the Running histogram check box is not selected, the 2-D Histogram block computes the frequency distribution of the current input.
When you set the Find the histogram over parameter
to Each column, the 2-D Histogram block
computes a histogram for each column of the M-by-N matrix
independently. The block outputs an n-by-N matrix,
where n is the Number of bins you
specify. The jth column of the output matrix contains
the histogram for the data in the jth column of
the M-by-N input matrix.
When you set the Find the histogram over parameter
to Entire input, the 2-D Histogram block
computes the frequency distribution for the entire input vector, matrix
or N-D array. The block outputs an n-by-1 vector,
where n is the Number of bins you
specify.
Running Operation
When you select the Running histogram check box, the 2–D Histogram block computes the frequency distribution of both the past and present data for successive inputs. The block resets the histogram (by emptying all of the bins) when it detects a reset event at the optional Rst port. See Resetting the Running Histogram for more information on how to trigger a reset.
When you set the Find the histogram over parameter
to Each column, the 2-D Histogram block
computes a running histogram for each column of the M-by-N matrix.
The block outputs an n-by-N matrix,
where n is the Number of bins you
specify. The jth column of the output matrix contains
the running histogram for the jth column of the M-by-N input
matrix.
When you set the Find the histogram over parameter
to Entire input, the 2-D Histogram block
computes a running histogram for the data in the first dimension of
the input. The block outputs an n-by-1 vector,
where n is the Number of bins you
specify.
Note
When the 2-D Histogram block is used in running mode and the
input data type is non-floating point, the output of the histogram
is stored as a uint32 data type. The largest number
that can be represented by this data type is 232-1.
If the range of the uint32 data type is exceeded,
the output data will wrap back to 0.
Resetting the Running Histogram
The block resets the running histogram whenever a reset event is detected at the optional Rst port. The reset signal and the input data signal must be the same rate.
You specify the reset event using the Reset port menu:
None— Disables the Rst port
Rising edge— Triggers a reset operation when the Rst input does one of the following:Rises from a negative value to a positive value or zero
Rises from zero to a positive value, where the rise is not a continuation of a rise from a negative value to zero (see the following figure)
Falling edge— Triggers a reset operation when theRstinput does one of the following:Falls from a positive value to a negative value or zero
Falls from zero to a negative value, where the fall is not a continuation of a fall from a positive value to zero (see the following figure)
Either edge— Triggers a reset operation when theRstinput is aRising edgeorFalling edge(as described earlier)Non-zero sample— Triggers a reset operation at each sample time that theRstinput is not zero
Parameters
- Lower limit of histogram
Enter a real-valued scalar for the lower boundary, Bm, of the lowest-valued bin.
NaNandinfare not valid values for Bm. Tunable.- Upper limit of histogram
Enter a real-valued scalar for the upper boundary, BM, of the highest-valued bin.
NaNandinfare not valid values for BM. Tunable.- Number of bins
The number of bins, n, in the histogram.
- Find the histogram over
Specify whether the block finds the histogram over the entire input or along each column of the input.
Note
The option will be removed in a future release.
- Normalized
When selected, the output vector, v, is normalized such that sum(v) = 1.
Use of this parameter is not supported for fixed-point signals.
- Running histogram
Set to enable the running histogram operation, and clear to enable basic histogram operation. For more information, see Basic Operation and Running Operation.
- Reset port
The type of event that resets the running histogram. For more information, see Resetting the Running Histogram. The reset signal and the input data signal must be the same rate. This parameter is enabled only when you select the Running histogram check box. For more information, see Running Operation.
Note
The fixed-point parameters listed are only used for fixed-point complex inputs, which are distributed by squared magnitude.
- Rounding mode
Select the Rounding Modes for fixed-point operations.
- Saturate on integer overflow
Select the overflow mode for fixed-point operations. See Precision and Range.
- Product output data type
Specify the product output data type. See Multiplication Data Types for illustrations depicting the use of the product output data type. You can set it to:
A rule that inherits a data type, for example,
Inherit: Inherit via internal ruleAn expression that evaluates to a valid data type, for example,
fixdt([],16,0)
Click the Show data type assistant button
to display the Data
Type Assistant, which helps you set the Product
output data type parameter.See Specify Data Types Using Data Type Assistant (Simulink) for more information.
- Accumulator data type
Specify the accumulator data type. You can set this parameter to:
A rule that inherits a data type, for example,
Inherit: Inherit via internal ruleAn expression that evaluates to a valid data type, for example,
fixdt([],16,0)
Click the Show data type assistant button
to display the Data
Type Assistant, which helps you set the Accumulator
data type parameter.See Specify Data Types Using Data Type Assistant (Simulink) for more information.
Supported Data Types
| Port | Supported Data Types |
|---|---|
In |
|
Output |
|
Rst |
|
See Also
histogram | MATLAB |