getPrevious, prev

Previous value of data

Since R2022a

Syntax

z = getPrevious(u)

z = prev(u)

Description

z = getPrevious(u) returns the value of the data at the previous time step. This operator works only in the Requirements Table block.

z = prev(u) is an alternative way to execute getPrevious(u).

Input Arguments

u — Data

block data

Data, specified as data defined in the Requirements Table block. See Define Data in Requirements Table Blocks. u must be specified as input or output data.

Output Arguments

z — Value at previous time step

any data type, depending on the input

Value at the previous time step, returned as a value with the same data type of u.

Examples

Check Previous Data Values

At the start time, set y equal to 0. After the start time, recall the value of the input data u in the precondition at the previous time step. One requirement checks if the previous value of u is greater than or equal to the current value, and another checks if the previous value is less than the current value. The block assigns different values for the output data y.

Tips

• If getPrevious attempts to return the value of the data at a time step when it was not defined, it returns an undefined value. For example, data is not defined before the simulation time is 0. For this situation, use the isStartup operator to define additional requirements at a simulation time of 0 and ~isStartup at the other time steps.

• You can use this operator only in the Requirements tab.

Version History

Introduced in R2022a