# LostTech.TensorFlow : API Documentation

Type HalfNormal

Namespace tensorflow.contrib.distributions

Parent Distribution

Interfaces IHalfNormal

The Half Normal distribution with scale `scale`.

#### Mathematical details

The half normal is a transformation of a centered normal distribution. If some random variable `X` has normal distribution, ```none X ~ Normal(0.0, scale) Y = |X| ``` Then `Y` will have half normal distribution. The probability density function (pdf) is:

```none pdf(x; scale, x > 0) = sqrt(2) / (scale * sqrt(pi)) * exp(- 1/2 * (x / scale) ** 2) ) ``` Where `scale = sigma` is the standard deviation of the underlying normal distribution.

#### Examples

Examples of initialization of one or a batch of distributions.
Show Example
```import tensorflow_probability as tfp
tfd = tfp.distributions  # Define a single scalar HalfNormal distribution.
dist = tfd.HalfNormal(scale=3.0)  # Evaluate the cdf at 1, returning a scalar.
dist.cdf(1.)  # Define a batch of two scalar valued HalfNormals.
# The first has scale 11.0, the second 22.0
dist = tfd.HalfNormal(scale=[11.0, 22.0])  # Evaluate the pdf of the first distribution on 1.0, and the second on 1.5,
# returning a length two tensor.
dist.prob([1.0, 1.5])  # Get 3 samples, returning a 3 x 2 tensor.
dist.sample([3]) ```

### Public properties

#### objectscale get;

Distribution parameter for the scale.

#### objectscale_dyn get;

Distribution parameter for the scale.