""" Calculate joint probability distribution https://en.wikipedia.org/wiki/Joint_probability_distribution """ def joint_probability_distribution( x_values: list[int], y_values: list[int], x_probabilities: list[float], y_probabilities: list[float], ) -> dict: """ >>> joint_distribution = joint_probability_distribution( ... [1, 2], [-2, 5, 8], [0.7, 0.3], [0.3, 0.5, 0.2] ... ) >>> from math import isclose >>> isclose(joint_distribution.pop((1, 8)), 0.14) True >>> joint_distribution {(1, -2): 0.21, (1, 5): 0.35, (2, -2): 0.09, (2, 5): 0.15, (2, 8): 0.06} """ return { (x, y): x_prob * y_prob for x, x_prob in zip(x_values, x_probabilities) for y, y_prob in zip(y_values, y_probabilities) } # Function to calculate the expectation (mean) def expectation(values: list, probabilities: list) -> float: """ >>> from math import isclose >>> isclose(expectation([1, 2], [0.7, 0.3]), 1.3) True """ return sum(x * p for x, p in zip(values, probabilities)) # Function to calculate the variance def variance(values: list[int], probabilities: list[float]) -> float: """ >>> from math import isclose >>> isclose(variance([1,2],[0.7,0.3]), 0.21) True """ mean = expectation(values, probabilities) return sum((x - mean) ** 2 * p for x, p in zip(values, probabilities)) # Function to calculate the covariance def covariance( x_values: list[int], y_values: list[int], x_probabilities: list[float], y_probabilities: list[float], ) -> float: """ >>> covariance([1, 2], [-2, 5, 8], [0.7, 0.3], [0.3, 0.5, 0.2]) -2.7755575615628914e-17 """ mean_x = expectation(x_values, x_probabilities) mean_y = expectation(y_values, y_probabilities) return sum( (x - mean_x) * (y - mean_y) * px * py for x, px in zip(x_values, x_probabilities) for y, py in zip(y_values, y_probabilities) ) # Function to calculate the standard deviation def standard_deviation(variance: float) -> float: """ >>> standard_deviation(0.21) 0.458257569495584 """ return variance**0.5 if __name__ == "__main__": from doctest import testmod testmod() # Input values for X and Y x_vals = input("Enter values of X separated by spaces: ").split() y_vals = input("Enter values of Y separated by spaces: ").split() # Convert input values to integers x_values = [int(x) for x in x_vals] y_values = [int(y) for y in y_vals] # Input probabilities for X and Y x_probs = input("Enter probabilities for X separated by spaces: ").split() y_probs = input("Enter probabilities for Y separated by spaces: ").split() assert len(x_values) == len(x_probs) assert len(y_values) == len(y_probs) # Convert input probabilities to floats x_probabilities = [float(p) for p in x_probs] y_probabilities = [float(p) for p in y_probs] # Calculate the joint probability distribution jpd = joint_probability_distribution( x_values, y_values, x_probabilities, y_probabilities ) # Print the joint probability distribution print( "\n".join( f"P(X={x}, Y={y}) = {probability}" for (x, y), probability in jpd.items() ) ) mean_xy = expectation( [x * y for x in x_values for y in y_values], [px * py for px in x_probabilities for py in y_probabilities], ) print(f"x mean: {expectation(x_values, x_probabilities) = }") print(f"y mean: {expectation(y_values, y_probabilities) = }") print(f"xy mean: {mean_xy}") print(f"x: {variance(x_values, x_probabilities) = }") print(f"y: {variance(y_values, y_probabilities) = }") print(f"{covariance(x_values, y_values, x_probabilities, y_probabilities) = }") print(f"x: {standard_deviation(variance(x_values, x_probabilities)) = }") print(f"y: {standard_deviation(variance(y_values, y_probabilities)) = }")