mindspore.nn.probability.distribution.StudentT
- class mindspore.nn.probability.distribution.StudentT(df=None, mean=None, sd=None, seed=None, dtype=mstype.float32, name='StudentT')[source]
StudentT distribution. A StudentT distribution is a continuous distribution with the range \([-\inf, \inf)\) and the probability density function:
\[f(x, \nu, \mu, \sigma) = (1 + y^2 / \nu)^{(-0.5*(\nu + 1))} / Z\]- where \(y = (x-\mu)/\sigma\), \(Z = abs(\sigma)*\sqrt(\nu * \pi)*\Gamma(0.5 * \nu)/\Gamma(0.5*(\nu + 1))\),
\(\nu, \mu, \sigma\) are the degrees of freedom , mean and scale of the laplace distribution respectively.
- Parameters
df (int, float, list, numpy.ndarray, Tensor) – The degrees of freedom. Default: None.
mean (int, float, list, numpy.ndarray, Tensor) – The mean of the distribution. Default: None.
sd (int, float, list, numpy.ndarray, Tensor) – The standard deviation of the distribution. Default: None.
seed (int) – The seed used in sampling. The global seed is used if it is None. Default: None.
dtype (mindspore.dtype) – The type of the event samples. Default: mstype.float32.
name (str) – The name of the distribution. Default: ‘StudentT’.
Note
df must be greater than zero.
sd must be greater than zero.
dist_spec_args are mean and sd.
dtype must be a float type because StudentT distributions are continuous.
- Raises
ValueError – When df <= 0.
ValueError – When sd <= 0.
TypeError – When the input dtype is not a subclass of float.
- Supported Platforms:
CPU
Examples
>>> import mindspore >>> import mindspore.nn as nn >>> import mindspore.nn.probability.distribution as msd >>> from mindspore import Tensor >>> # To initialize a StudentT distribution of the df 2.0, the mean 3.0 and the standard deviation 4.0. >>> n1 = msd.StudentT(2.0, 3.0, 4.0, dtype=mindspore.float32) >>> # A StudentT distribution can be initialized without arguments. >>> # In this case, `df`, `mean` and `sd` must be passed in through arguments. >>> n2 = msd.StudentT(dtype=mindspore.float32) >>> # Here are some tensors used below for testing >>> value = Tensor([1.0, 2.0, 3.0], dtype=mindspore.float32) >>> df_a = Tensor([2.0], dtype=mindspore.float32) >>> mean_a = Tensor([2.0], dtype=mindspore.float32) >>> sd_a = Tensor([2.0, 2.0, 2.0], dtype=mindspore.float32) >>> df_b = Tensor([1.0], dtype=mindspore.float32) >>> mean_b = Tensor([1.0], dtype=mindspore.float32) >>> sd_b = Tensor([1.0, 1.5, 2.0], dtype=mindspore.float32) >>> ans = n1.log_prob(value) >>> print(ans.shape) (3,) >>> # Evaluate with respect to the distribution b. >>> ans = n1.log_prob(value, df_b, mean_b, sd_b) >>> print(ans.shape) (3,) >>> # `mean` and `sd` must be passed in during function calls >>> ans = n2.log_prob(value, df_a, mean_a, sd_a) >>> print(ans.shape) (3,)
- log_prob(value, df=None, mean=None, sd=None)
the log value of the probability.
Parameters
value (Tensor) - the value to compute.
df (Tensor) - the degrees of freedom of the distribution. Default: None.
mean (Tensor) - the mean of the distribution. Default: None.
sd (Tensor) - the standard deviation of the distribution. Default: None.
Returns
Tensor, the log value of the probability.