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How is the Softmax activation function used?

by Nathan Zachary
softmax activation function

Mathematically speaking, the softmax activation function goes under a few different names. Combining sigmoid functions creates Softmax. A data point’s category can be deduced from a sigmoid function’s value between zero and one. Binary classification issues often use Sigmoid functions.

Softmax can handle multiple-class problems concurrently. The softmax activation function yields class membership probabilities.

In deep learning, logits are the unprocessed prediction values generated by the final neuron layer of the neural network for the classification task and are represented as real numbers in the range [-infinity, +infinity]. “Encyclopedia Britannica”

We’ll examine the softmax activation function in detail here to learn more about it. It divides big groups. Why can’t multi-class neural networks use distinct activation functions?

What, precisely, do we mean when we talk about logits?

The last layer of a neural network outputs logit scores.

SoftMax’s purpose is unknown.

By adding the exponents of each output and then normalizing each number by the sum of those exponents, the softmax activation function converts the logit values into probabilities, with the total output vector equaling 1. The softmax activation function equation is similar to the sigmoid function equation, except the raw output is summed in the denominator. To rephrase, we can’t just use z1 as-is when calculating the value of softmax on a single raw output. Look at the denominator and you’ll see that z1, z2, z3, and z4 all need to be there.

Using the softmax activation function, we can be sure that the sum of our probability estimates will always equal 1. To increase the likelihood that a given example is classified as “airplane,” we must decrease the likelihoods that the same example is classified as “dog,” “cat,” “boat,” or “other” when using a softmax activation function on our outputs to distinguish between classes like “airplane,” “dog,” “cat,” “boat,” and “other.” In the future, we will have access to an identical example.

we will compare the sigmoid and softmax functions’ outputs.

The accompanying graph shows the striking similarity between the graphs of the sigmoid and softmax activation function.

The softmax activation function has applications in multiple categorization methods and neural networks. When compared to the max, softmax is preferable because it does not immediately exclude any numbers that fall short. Since the SoftMax function’s denominator incorporates all components of the original output value, the various probabilities returned by the function are related to one another.

In the specific case of binary classification, the Sigmoid equation looks like this:

The equation proves that a Sigmoid function can be used for Softmax binary classification.

When building a network to solve a multiclass problem, the number of neurons in the output layer should be equal to the number of classes in the target.

Therefore, the number of classes determines the number of neuronal ensembles in the output layer.

To illustrate, let’s pretend the neurons have transmitted a signal consisting of the numbers [0.7, 1.5, 4.8].

The values [0.01573172, 0.03501159, 0.94925668] are the result of applying the softmax activation function to the output of a neural computation.

These results depict the probabilities of various data kinds. There will always be exactly one result from all inputs.

To further understand the softmax activation function, let’s have a look at an example.

Application of Softmax to the Real World.

To see how softmax activation functions, consider the following illustration.

The above scenario is an attempt to determine whether or not the provided image represents a dog, cat, boat, or airplane.

But first, let’s see if the decision made by our softmax activation function is the correct one.

The preceding graph shows this. I have separated the output of our scoring function f into its constituent parts for each of the four classes shown here. We have calculated the log probabilities for each of the four groups, but they have not been normalized.

I have arbitrarily selected the points values used in this illustration. In practice, though, you won’t be using random numbers but rather the output of your scoring function f.

Exponentially increasing the scoring function’s output unnormalizes probabilities.

Add the denominator exponents and divide by the sum to calculate class probability.

Using the inverse logarithm, one can determine the total amount of money lost. Finally, we can see that our Softmax classifier correctly identified the preceding case’s image as an “airplane” with a confidence score of 93.15%. 

Let’s have a look at a simple example of the softmax activation function implementation in Python.


We discovered that the softmax activation function that transforms the neural network’s output layer’s inputs and outputs into a discrete probability distribution over the target classes. Softmax distributions have the properties of having nonnegative probability and a sum of 1.

Thanks to this article, you are aware of the significance of the. InsideAIML has blogs and courses on data science, machine learning, AI, and cutting-edge technology.

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