Solving the Matlab batch not passing arguments to function Error

Learn how to effectively use the `batch` command in Matlab to pass arguments to your custom functions and resolve common errors.
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Understanding the Matlab batch not passing arguments to function Issue

When working with Matlab, particularly for users who are relatively new to the platform, it’s not uncommon to encounter various errors, especially while trying to execute custom functions in a batch mode. One such issue arises when attempting to pass arguments to a custom function using the batch command.

This blog will cover a common problem that many users face and provide a clear solution to overcome it.

The Problem

A user attempted to run a simple standalone function named runTest with the intent of executing it in a batch context. Here’s a simplified version of the situation laid out:

The function runTest is designed to create an array of zeros based on the input dimensions provided.

[[See Video to Reveal this Text or Code Snippet]]

When testing the function directly, it worked perfectly:

[[See Video to Reveal this Text or Code Snippet]]

However, when they attempted to run it in batch mode:

[[See Video to Reveal this Text or Code Snippet]]

They received an error stating:

[[See Video to Reveal this Text or Code Snippet]]

This leads to the question: Why does calling the function in batch mode result in an error when it works perfectly fine in a direct call?

The Explanation

The key issue arises from how Matlab processes function calls.

When you call a function without the means of a handle (like -), Matlab interprets the call as an instance where it should execute the function immediately. Thus, the call effectively becomes runTest() without any arguments, which leads to the "not enough input arguments" error.

In simpler terms, you're inadvertently telling Matlab to execute runTest without the inputs needed for it to function properly.

The Solution

The solution to this dilemma is quite straightforward: you must use a function handle. Using the - symbol before the function name tells Matlab to treat runTest as a function handle that can be executed later with the specified inputs.

Here’s how to fix the batch command:

Instead of this:

[[See Video to Reveal this Text or Code Snippet]]

You should write:

[[See Video to Reveal this Text or Code Snippet]]

By doing so, Matlab can properly queue your function for execution with the provided arguments when it processes the batch job.

Conclusion

Navigating Matlab's batch processing can be tricky, especially for newcomers. The takeaway here is to ensure that you are using function handles when passing custom functions to batch commands. Always remember to use the - symbol before your function name when executing it in batch mode.

By following the guidance above, users can avoid the "not enough input arguments" error and streamline their use of custom functions within Matlab’s powerful batch processing options.

Happy coding in Matlab, and remember: when in doubt, always check how your functions are being called!