Gaussian Log-Likelihood

~20 mincode completion

Implement gaussian_log_likelihood(x, mu, sigma) that returns the total (summed) log-likelihood over all observations in x.

Examples

Single point at the mean: maximum log-likelihood for sigma=1

Input
gaussian_log_likelihood([0], 0, 1)
Output
-0.91894

Two points equidistant from mean

Input
gaussian_log_likelihood([-1, 1], 0, 1)
Output
-2.83788

Larger sigma reduces log-likelihood at mean

Input
gaussian_log_likelihood([0], 0, 2)
Output
-1.61209

Hints

Hint 1

is the natural log, which is what this formula wants.

Hint 2

Do not forget to log sigma term. That step is easy to skip.

Requirements

  • x: Observations, 1D array

  • mu: Mean of the Gaussian

  • sigma: Standard deviation of the Gaussian (> 0)

  • Return Total log-likelihood (sum over all observations).

Constraints

  • Allowed library: NumPy only

  • Time limit: 200 ms, Memory: 64 MB

Where this shows up

~20 min

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Python
import numpy as np

def gaussian_log_likelihood(x: np.ndarray, mu: float, sigma: float) -> float:
    """
    Compute the total log-likelihood of data under a Gaussian distribution.

    Args:
        x:     Observations, 1D array
        mu:    Mean of the Gaussian
        sigma: Standard deviation of the Gaussian (> 0)

    Returns:
        Total log-likelihood (sum over all observations).
    """
    # YOUR CODE HERE
    pass
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