tf.math.sigmoid

TensorFlow 1 version

View source on GitHub

Computes sigmoid of x element-wise.

tf.math.sigmoid(
    x, name=None
)

Formula for calculating $\mathrm{sigmoid}(x) = y = 1 / (1 + \exp(-x))$.

For $x \in (-\infty, \infty)$, $\mathrm{sigmoid}(x) \in (0, 1)$.

Example Usage:

If a positive number is large, then its sigmoid will approach to 1 since the formula will be y = <large_num> / (1 + <large_num>)

x = tf.constant([0.0, 1.0, 50.0, 100.0])
tf.math.sigmoid(x)
<tf.Tensor: shape=(4,), dtype=float32,
numpy=array([0.5      , 0.7310586, 1.       , 1.       ], dtype=float32)>

If a negative number is large, its sigmoid will approach to 0 since the formula will be y = 1 / (1 + <large_num>)

x = tf.constant([-100.0, -50.0, -1.0, 0.0])
tf.math.sigmoid(x)
<tf.Tensor: shape=(4,), dtype=float32, numpy=
array([0.0000000e+00, 1.9287499e-22, 2.6894143e-01, 0.5],
      dtype=float32)>

Usage Example:

x = tf.constant([-128.0, 0.0, 128.0], dtype=tf.float32)
tf.sigmoid(x)
<tf.Tensor: shape=(3,), dtype=float32,
numpy=array([0. , 0.5, 1. ], dtype=float32)>