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Custom Mapping for External Inputs of a Model

This example shows how to create a custom mapping function for the Root Inport Mapping tool. The Root Inport Mapping tool associates MAT-file data with a specific input port, based on one of these criteria.

  • Index - Maps in the order it appears in the file to the corresponding port number.

  • Block Name - Maps by variable name to the corresponding root inport with the matching block name.

  • Signal Name - Maps by variable name to the corresponding root inport with the matching signal name.

  • Block Path - Maps by the BlockPath parameter to the corresponding root inport with the matching block path.

  • Custom - Maps using a MATLAB function.

Use a custom mapping criteria when the data you are trying to map does not match any of the other mapping criteria.

Custom Mapping Scenario

If the combination of input data and the model input ports does not match Index, Block Name, Signal Name, or Block Path mapping criteria, you can do one of the following:

  • Rename the input data in the MAT-file

  • Rename the input ports on the model

  • Use the custom mapping mode

This example shows how to write a custom mapping function.

The workflow described below includes

  • Create a MATLAB File to contain the custom mapping function

  • Declare the custom mapping function name, inputs, and outputs

  • Initialize the output for assignment of the return value

  • Define and implement your mapping algorithm

  • Validate your mapping algorithm

Create a New MATLAB Function File

Create a MATLAB function file. This file will contain your custom mapping function.

Declare Custom Mapping Function

Declare a custom mapping function name, and specify the inputs and outputs. slexCustomMappingMyCustomMapslexCustomMappingMyCustomMap is the custom mapping function in this example. It declares the function inputs and outputs as defined below.


  • modelName - String that contains the model name.

  • signalNames - Cell array of strings that contain variable names of signals to map

  • signals - Cell array of signal data aligned with signalNames such that signalNames{1} is the variable name of the signal stored in signals{1}.


  • inputMap - Array or scalar of objects that result from the getRootInportMap function.

Initialize the Output

Initialize the value of the output variable inputMap. To do this use the getRootInportMap command with the empty property as shown in the example function slexCustomMappingMyCustomMapslexCustomMappingMyCustomMap or in the code snippet below. This initializes the output variable to empty so that a value can be assigned to the output.

inputMap = getRootInportMap('empty');

Define Your Custom Mapping Algorithm

Things to think about when defining your custom mapping algorithm.

  • What is the criteria for mapping signals to a root-level inport , for example BlockName mapping matches the name of the input signal to the name of the root-level inport block name.

  • What information is needed to create a mapping.

  • What happens if the mapping criteria determines that there is no match between signal and root-level inport.

The example addresses these items by

  • Using the root-level port number and signal name for mapping criteria.

  • Including a logical condition to handle the case where there is no match between port number and signal name.

Implement Your Mapping Algorithm

Next, implement your mapping algorithm.

In the slexCustomMappingMyCustomMapslexCustomMappingMyCustomMap implementation, the root-level inport port number is the mapping criteria criteria. The algorithm gets this port number from the root-level inport block. It then gets the numerical values appended to the names of the signals that are passed into the function, and compares the port number with the numerical values.

NOTE: In addition to implementing your mapping algorithm, you should also include a logical statement to handle situations where a mapping is not possible. The example function does this by using an if statement with the isempty function to determine if a mapping can be made.

Create the Mapping

The final step is to use the getRootInportMap function to create a custom map. The getRootInportMap function uses Property-Value pairs to create a custom map. The properties are:

  • model - String that represents the model name.

  • signalName - String or cell of strings that contains the value of the variable name of the signal to map.

  • blockName - String or cell of strings that contains the value of the block name of the port to be mapped.

The following code is an example of this function. This same code appears in the example function slexCustomMappingMyCustomMapslexCustomMappingMyCustomMap.

inputMap = getRootInportMap(...

Validate the Custom Mapping Function

To validate the custom mapping function at the command line:

  1. Open the model against which you want to test your function.

  2. Create some input signals to support the model.

  3. Call your custom mapping function with the correct input parameters.

  4. Validate the expected input string to send to the sim command, or to place in the model configuration parameters External Input String edit box.

Execute the lines of code in the following example. This code uses the custom mapping function provided with this example. If the custom map function succeeds, you should see a comma-separated list of variable names displayed in the order of the port number to which they are assigned ('port1,port2').

port1               = timeseries(ones(10,1)*10);
port2               = timeseries(zeros(10,1));
inputMap            = slexCustomMappingMyCustomMap('slexAutotransRootInportsExample',{'port1' , 'port2'},{port1 , port2});
externalInputString = getInputString(inputMap,'base');
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