| Simulink® | |
Assign values to specified elements of signal
Math Operations
The Assignment block assigns values to specified elements of the signal. You can specify the indices of the elements to be assigned values either by entering the indices in the block's dialog box or by connecting an external indices source or sources to the block. The signal at the block's data port, labeled U, specifies values to be assigned to Y. The block replaces the specified elements of Y with elements from the data signal, leaving unassigned elements unchanged from their initial values. If the parameter Initialize output has a value of Initialize using input port <Y0>, the signal at the input port Y0 initializes the output. If this parameter is set to Specify size for each dimension in table, the Output Size parameter requires you to specify the size of the block's output signal. The parameter dialog box and the block's appearance change to reflect the number of dimensions of the output. The Initialize output parameter appears only if you select Index vector (port) or Starting index (port) for the Index Option parameter.
Based on the value you enter for the Number of output dimensions parameter, a table of index options is displayed. Each row of the table corresponds to one of the output dimensions in Number of output dimensions. For each dimension, you can define the elements of the signal to work with. Specify a vector signal as a 1-D signal and a matrix signal as a 2-D signal. When you configure the Assignment block for multidimensional signal operations, the block icon changes.
For example, assume a 5-D signal with a one-based index mode. The table in the Assignment block dialog changes to include one row for each dimension. If you define each dimension with the following entries:
1
Index Option, select Assign all
2
Index Option, select Index vector (dialog)
Index, enter [1 3 5]
3
Index Option, select Starting index (dialog)
Index, enter 4
4
Index Option, select Starting index (port)
5
Index Option, select Index vector (port)
The assigned values will be Y(1:end,[1 3 5],4:3+size(U,3),Idx4:Idx4+size(U,4)-1,Idx5)=U, where Idx4 and Idx5 are the input ports for dimensions 4 and 5.
The Assignment block's data port is labeled U. The rest of this section refers to the data port as U to simplify the explanation of the block's usage.
You can use the block to assign values to vector, matrix, or multidimensional signals.
You can use the Assignment block to assign values computed in a For or While Iterator loop to successive elements of a vector, matrix, or multidimensional signal in a single time step. For example, the following model uses a For Iterator block to create a vector signal each of whose elements equals 3*i where i is the index of the element.
Iterated assignment uses an iterator (For or While) block to generate the indices required by the Assignment block. On the first iteration of an iterated assignment, the Assignment block copies the first input (Y0) to the output (Y) and assigns the second input (U) to the output Y(E1). On successive iterations, the Assignment block simply assigns the current value of U to Y(Ei), i.e., without first copying Y0 to Y. All of this occurs in a single time step.
The data and initialization ports of the Assignment block accept signals of any data type supported by Simulink® software, including fixed-point data types. The external indices port accepts any built-in data type, except Boolean data types.
For a discussion on the data types supported by Simulink software, see Data Types Supported by Simulink®.
Enter the number of dimensions of the output signal.
Specifies the indexing mode: One-based or Zero-based. If One-based is selected, an index of 1 specifies the first element of the input vector, 2, the second element, and so on. If Zero-based is selected, an index of 0 specifies the first element of the input vector, 1, the second element, and so on.
Define, by dimension, how the elements of the signal are to be indexed. From the list, choose:
Assign all
This is the default. No further configuration is required. All elements are assigned.
Index vector (dialog)
Enables the Index column. Enter the index of the element.
Index vector (port)
No columns are enabled. If the Initialize output (Y) parameter is set to Initialize using input port <Y0>, the block initializes the output port Y with the input port Y0.
If the Initialize output (Y) parameter is set to Specify size for each dimension in table, enter the width of the block's output signal in the Output Size column.
Starting index (dialog)
Enables the Index column. Enter the starting index of the range of elements to be assigned values.
Starting index (port)
No columns are enabled. If the Initialize output (Y) parameter is set to Initialize using input port <Y0>, initializes the output port Y with the input port Y0.
If the Initialize output (Y) parameter is set to Specify size for each dimension in table, enter the width of the block's output signal in the Output Size column.
The Index and Output Size columns are displayed as relevant.
If the Index Option is Index vector (dialog), enter the index of each element you are interested in.
If the Index Option is Starting index (dialog), enter the starting index of the range of elements to be selected. The number of elements from the starting point is determined by the size of this dimension at U.
Enter the width of the block output signal. If you select Specify size for each dimension in table for the Initialize output (Y) parameter, this column is enabled.
Specify how to initialize the output signal.
Initialize using input port <Y0>
The signal at the input port Y0 initializes the output.
Specify size for each dimension in table
The block requires you to specify the width of the block's output signal in the Output Size parameter.
Specifies whether to produce a warning or error message if you have not assigned all output element. Options include:
Error
Warning
None
Specify the time interval between samples. To inherit the sample time, set this parameter to -1. See Specifying Sample Time.
Direct Feedthrough | Yes |
Sample Time | Specified by Sample time parameter |
Scalar Expansion | Yes |
Dimensionalized | Yes |
Multidimensionalized | Yes |
Zero Crossing | No |
| Assertion | Backlash | |
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