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Creating Custom Loss Functions:Top 3 Considerations

One of the most important building blocks of a machine learning model is the loss function, also known as the cost function. In data science, the loss function is used to determine the performance of a machine learning model for a single observation in a dataset:the lower the loss, the better the accuracy of the model. To visualize, the loss function is your map when you're at the top of the mountain looking for a way down the foothill. In other words, loss functions help to reduce errors to get as close as possible to the intended output of the machine.

ContentsCustom loss functionsConsiderations when creating a custom loss function1. Take arguments and return scalars2. Symmetry of risks3. Deep LearningFinal Thoughts

Custom Loss Functions

Loss functions that are frequently used in industry are easy to understand and are integrated into well-known deep learning frameworks, like Keras or Phyton. These built-in loss functions are effective for most common tasks, such as classification and regression. However, some activities cannot be properly handled using these built-in loss functions, hence the use of other losses that are better suited for that specific task. For this reason, a custom loss function is created which evaluates the difference between predicted and actual values ​​based on custom criteria.

Here are the rules to follow when creating a custom loss:

  • The loss function should accept only two arguments:the target value and the predicted value. You will need these values ​​because two quantities are needed to calculate the prediction error (loss).
  • The loss function should use the predicted value when calculating the loss. Otherwise, the gradient expression will not be set and you will receive an error.
  • Then just compile this function into the template.

Considerations when creating a custom loss function

If you're still not convinced that custom loss functions will be useful to you, here are three reasons why you should consider creating custom loss functions:

1. Take arguments and return scalars

You can create your own custom loss function, but it's also good to be aware of existing loss functions in deep learning frameworks like Keras. A custom loss function in Keras can improve the performance of a leaanneau model machine in any way you want, and it can be very beneficial for solving specific problems faster. Suppose you are developing an investment portfolio optimization model. In this scenario, it is appropriate to create a custom loss function with a huge penalty for predicting price moves in the wrong direction.

If you're using Keras, you can write a custom loss function that takes two arguments and returns a scalar:the true value and the predicted value. The custom loss function is then passed to the model. After that, compile the custom loss function as a parameter, like any other loss function.

To learn more about creating custom loss functions in Keras, continue reading this article.

2. Risk symmetry

Suppose you are at home and need to determine the time you will leave in order to be on time for an interview. You don't want to leave too early as you will have to wait for the interview and you may have to spend money on an expensive cup of coffee while you wait. You also don't want to arrive too late as you may be turned away for being unprofessional. Yet the risk of leaving too soon is much less than the risk of leaving too late – the cost of waiting is insignificant compared to the cost of unemployment. This is called risk asymmetry.

You can implement machine learning to determine when to leave the house. You can do this by addressing the risk asymmetry directly in an ML (machine learning) model using a custom loss function, which penalizes late errors more than early errors.

3. Deep learning

Deep learning can provide a simple solution to some kinds of challenges when training an ML model. Deep learning allows you to explore several built-in and custom loss functions that can be used with various bundled optimizers rather than creating a custom probability function and optimizer.

Some models learn from a graph of inputs and examples, and the loss function used must be relevant to the specific problem, such as classification or regression. In this way, custom loss functions can be useful in deep learning when developing regression models that need to make predictions for data of varying orders of magnitude. If so, you can create custom loss functions to predict house prices in an area where values ​​can vary widely.

Last thoughts

Sometimes the better a machine learning model predicts, it doesn't always mean it's better for the business. Indeed, there can be some confusion between data science metrics and business metrics. Therefore, a custom loss function is important to drive the machine learning model towards the same goal as the business goal.

As you can see, applying custom loss functions to your machine learning model can improve the performance of a machine learning model as desired, making it more useful for solving specific problems. machine learning.