Pad

Pad or truncate specified dimension(s)

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Libraries:
DSP System Toolbox / Signal Operations

Description

The Pad block extends or crops the dimensions of an input signal by padding or truncating along its columns, rows, columns and rows, or along any other dimension(s) that you specify. The block truncates the input when you specify output dimensions that are shorter than the corresponding input dimensions. If the input and output lengths are the same, the block acts as a pass-through.

You can enter the pad value in the block mask or via an input port. You can enter output sizes in the block mask, or have the block pad the specified dimensions until their length is the next highest power of two. The Pad signal at parameter controls whether the block pads or truncates the input signal dimensions at the beginning, end, or both. For odd pad or truncation lengths, the extra pad or truncation value is applied at the end of the signal. When the block is in the Specified dimensions mode, you can specify either the output size or the pad size.

You can configure the block to warn or error when an input signal is truncated using the Action when truncation occurs parameter.

Examples

Pad or Truncate Matrix with Constant Values

Use the Pad block to pad or truncate constant values to a matrix.

Open Model

Ports

Input

Input 1 — Data input

scalar | vector | matrix | N-D array

Specify the input as a scalar, vector, matrix, or an N-D array.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | bus
Complex Number Support: Yes

Output

Output 1 — Padded or truncated output

scalar | vector | matrix | N-D array

Output of the Pad block. The size and dimension of the output depends on whether the block has padded or truncated the input along the specified dimension. The data type and complexity of the output matches that of the input.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | bus
Complex Number Support: Yes

Parameters

Pad over — Dimension over which to pad or truncate

Columns (default) | Rows | Columns and rows | None | Specified dimensions

Specify the dimensions over which to pad or truncate:

• Columns

• Rows

• Columns and rows

• None

• Specified dimensions

Dimensions to pad — Specify dimension over which to pad or truncate

1 (default) | scalar | vector

Specify the one-based dimension(s) over which to pad or truncate. The value for this parameter can be a scalar or a vector. For example, specify 1 to pad columns. Specify [1 2] to pad columns and rows. Specify [1 3 5] to pad the first, third, and fifth dimensions.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions.

Pad value source — Source of pad value

Specify via dialog (default) | Input port

Choose how you specify the pad value. The pad value can come from the dialog or from an input port:

• If you select Specify via dialog, the Pad value parameter appears.

• If you select Input port, the PVal port appears on the block icon.

Pad value — Pad value

0 (default) | scalar

Specify the constant scalar value with which to pad the input.

Tunable: Yes

Dependencies

This parameter appears only when you set Pad value source to Specify via dialog.

Output column mode — Mode of specifying column length

User-specified | Next power of two

Choose how you specify the column length of the output:

• If you select User-specified, the Column size parameter appears.

• If you select Next power of two, the block pads the output columns until their length is the next highest power of two. If the column length is already a power of two, the block does not pad the columns.

Dependencies

This parameter appears only when you set Pad over to Columns or Columns and rows.

Column size — Column length of output

1 | scalar

Specify the column length of the output. If the specified column length is longer than the input column length, the block pads the columns. If the specified column length is shorter than the input column length, the block truncates the columns.

Dependencies

This parameter appears only when you set Output column mode to User-specified.

Output row mode — Mode of specifying row length

User-specified (default) | Next power of two

Choose how you specify the row length of the output:

• If you select User-specified, the Row size parameter appears.

• If you select Next power of two, the block pads the output rows until their length is the next highest power of two. If the row length is already a power of two, the block does not pad the rows.

Dependencies

This parameter appears only when you set Pad over to Rows or Columns and rows.

Row size — Row length of output

1 | scalar

Specify the row length of the output. If the specified row length is longer than the input row length, the block pads the rows. If the specified row length is shorter than the input row length, the block truncates the rows.

Dependencies

This parameter appears only when you set Output row mode to User-specified.

Specify — Specify output size or pad size

Output size (default) | Pad size

Choose whether you want to control the output length of the specified dimensions by specifying the output size or the pad size.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions.

Output size mode — Mode of specifying output length

User-specified | Next power of two

Choose how you specify the output length of the specified dimensions:

• If you select User-specified, the Output size parameter appears.

• If you select Next power of two, the block pads the specified dimensions until their length is the next highest power of two. If the dimension length is already a power of two, the block does not pad in that dimension.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Output size.

Output size — Output length along specified dimension

1 | scalar | vector

Specify the output length of the specified dimension(s). This parameter must be a scalar or a vector with the same number of elements as the Dimensions to pad parameter. Each element in the Output size vector gives the output length for the corresponding dimension in the Dimensions to pad vector. If the specified length is longer than the input length for a given dimension, the block pads that dimension. If the specified length is shorter than the input length for a given dimension, the block truncates that dimension.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Output size.

Pad size at beginning — Specify number of values to add to beginning of input signal

0 | scalar | vector

Specify how many values to add to the beginning of the input signal along the specified dimension(s). This parameter must be a scalar or a vector with the same number of elements as the Dimensions to pad parameter. Each element in the Pad size at beginning parameter gives the pad length at the beginning of the corresponding dimension in the Dimensions to pad parameter. Values of this parameter must be nonnegative integers.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Pad size.

Pad size at end — Specify number of values to add to end of input signal

0 | scalar | vector

Specify how many values to add to the end of the input signal along the specified dimension(s). This parameter must be a scalar or a vector with the same number of elements as the Dimensions to pad parameter. Each element in the Pad size at end parameter gives the pad length at the end of the corresponding dimension in the Dimensions to pad parameter. Values of this parameter must be nonnegative integers.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Pad size.

Pad signal at — Specify where to pad or truncate signal

End (default) | Beginning | Beginning and end

Specify whether to pad or truncate the signal at the Beginning, End, or Beginning and end of the specified dimension(s). When you select Beginning and end, half the pad length is added to the beginning of the signal and the other half is added to the end of the signal. For an odd pad length, the extra value is added to the end of the signal. When you specify to truncate the signal in this mode, an equal number of values are truncated from the beginning and the end of the signal. In the case of an odd truncation length, the extra value is removed from the end of the signal.

Dependencies

This parameter appears only when you set Pad over to Columns, Rows, and Columns and rows.

Action when truncation occurs — Action to take when truncation occurs

None | Warning | Error

Specify the action the block takes when it truncates the input.

• None –– The block does not notify when the input is truncated.

• Warning –– The block displays a warning when the input is truncated.

• Error –– The block displays an error message and terminates the simulation when the input is truncated.

Dependencies

This parameter appears only when you set Pad over to Columns, Rows, and Columns and rows.

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Generated code relies on the memcpy or memset function (string.h) under certain conditions.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced before R2006a