Array-Vector Subtract

Subtract vector from array along specified dimension

Library

Math Functions / Matrices and Linear Algebra / Matrix Operations

dspmtrx3

Description

The Array-Vector Subtract block subtracts the values in the input vector V from the values in the specified dimension of the N-dimensional input array A.

The length of the input V must be the same as the length of the specified dimension of A. The Array-Vector Subtract block subtracts each element of V from the corresponding element along that dimension of A.

Consider a 3-dimensional M-by-N-by-P input array A(i,j,k) and a N-by-1 input vector V. When the Subtract along dimension parameter is set to 2, the output of the block Y(i,j,k) is

Y(i,j,k)=A(i,j,k)V(j)

where

1iM1jN1kP

The output of the Array-Vector Subtract block is the same size as the input array, A. This block accepts real and complex floating-point and fixed-point inputs.

Fixed-Point Data Types

The following diagram shows the data types used within the Array-Vector Subtract block for fixed-point signals.

When you specify the vector V on the Main pane of the block mask, you must specify the data type and scaling properties of its elements in the Vector (V) parameter on the Data Types tab. When the vector comes in through the block port, its elements inherit their data type and scaling from the driving block.

The output of the subtractor is in the accumulator data type.

You can set the vector, accumulator, and output data types in the block dialog as discussed below.

Dialog Box

The Main pane of the Array-Vector Subtract block dialog appears as follows.

Subtract along dimension

Specify the dimension along which to subtract the elements of vector V from the input array A.

Vector (V) source

Specify the source of the vector, V. The vector can come from the Input port or from a Dialog parameter.

Vector (V)

Specify the vector, V. This parameter is visible only when you select Dialog parameter for the Vector (V) source parameter.

The Data Types pane of the Array-Vector Subtract block dialog appears as follows.

    Note:   Floating-point inheritance takes precedence over the data type settings defined on this pane. When inputs are floating point, the block ignores these settings, and all internal data types are floating point.

Rounding mode

Select the rounding mode for fixed-point operations.

    Note:   The Rounding mode and Overflow mode settings have no effect on numerical results when both of the following conditions exist:

    • Accumulator data type is Inherit: Inherit via internal rule

    • Output data type is Inherit: Same as accumulator

    With these data type settings, the block is effectively operating in full precision mode.

Overflow mode

Select the overflow mode for fixed-point operations.

Vector (V)

Use this parameter to specify the word and fraction lengths for the elements of the vector, V. You can set this parameter to:

  • A rule that inherits a data type, for example, Inherit: Same word length as input

  • An expression that evaluates to a valid data type, for example, fixdt(1,16,0)

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 for more information.

    Note   The Vector (V) parameter on the Data Types pane is only visible when you select Dialog parameter for the Vector (V) source parameter on the Main pane of the block mask. When the vector comes in through the block's input port, the data type and scaling of its elements are inherited from the driving block.

Accumulator data type

Specify the accumulator data type. See Fixed-Point Data Types for illustrations depicting the use of the accumulator data type in this block. You can set this parameter to:

  • A rule that inherits a data type, for example, Inherit: Inherit via internal rule

  • An expression that evaluates to a valid data type, for example, fixdt(1,16,0)

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 for more information.

Output data type

Specify the output data type. See Fixed-Point Data Types for illustrations depicting the use of the output data type in this block. You can set it to:

  • A rule that inherits a data type, for example, Inherit: Same as accumulator

  • An expression that evaluates to a valid data type, for example, fixdt(1,16,0)

Click the Show data type assistant button to display the Data Type Assistant, which helps you set the Output data type parameter.

See Specify Block Output Data Types for more information.

Minimum

Specify the minimum value that the block should output. The default value is [] (unspecified). Simulink® software uses this value to perform:

  • Simulation range checking (see Signal Ranges)

  • Automatic scaling of fixed-point data types

Maximum

Specify the maximum value that the block should output. The default value is [] (unspecified). Simulink software uses this value to perform:

  • Simulation range checking (see Signal Ranges)

  • Automatic scaling of fixed-point data types

Lock data type settings against changes by the fixed-point tools

Select this parameter to prevent the fixed-point tools from overriding the data types you specify on the block mask.

Supported Data Types

PortSupported Data Types

A

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed only)

  • 8-, 16-, and 32-bit signed integers

V

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed only)

  • 8-, 16-, and 32-bit signed integers

Output

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed only)

  • 8-, 16-, and 32-bit signed integers

See Also

Array-Vector AddDSP System Toolbox
Array-Vector DivideDSP System Toolbox
Array-Vector MultiplyDSP System Toolbox

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