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Basic Linear Regression Function

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Problem

Write a function that fits a basic simple linear regression model using ordinary least squares. Given paired training data x and y, compute the best-fit line y = m*x + b, then use it to predict outputs for a list of query values.

Formal Specification

Implement a function that takes:

  • x: a list of numbers representing the independent variable
  • y: a list of numbers representing the dependent variable
  • queries: a list of numbers to predict

Return a list of predicted values for each query, using the fitted line.

Use the least-squares formulas:

  • m = sum((xi - mean_x) * (yi - mean_y)) / sum((xi - mean_x)^2)
  • b = mean_y - m * mean_x

If all x values are identical, the slope is undefined. In that case, return the mean of y for every query.

Constraints

  • 2 <= len(x) == len(y) <= 10^5
  • 1 <= len(queries) <= 10^5
  • -10^9 <= x[i], y[i], queries[i] <= 10^9
  • Use ordinary least squares, not iterative optimization

Function Signature

def fit_linear_regression(x, y, queries):
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