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QuestionAnswer
OLS Linear Regression Weight Vector Formula w = (X^T * X)^-1 * X^T * t
Ridge Regression (L2 Regularization) Analytical Weights Formula w = (X^T * X + lambda * I)^-1 * X^T * t
Binary Logistic Regression Hypothesis Function (Sigmoid) y = sigma(w^T * phi) = 1 / (1 + exp(-w^T * phi))
Binary Logistic Regression Cross-Entropy Loss Function E(w) = - sum_{n=1}^N [ t_n * ln(y_n) + (1 - t_n) * ln(1 - y_n) ]
Multiclass Logistic Regression Hypothesis Function (Softmax) p(C_k | phi) = y_k(phi) = exp(w_k^T * phi) / sum_j exp(w_j^T * phi)
Multiclass Logistic Regression Negative Log-Likelihood Loss L(w_1, ..., w_K) = - sum_{n=1}^N sum_{k=1}^K t_{nk} * ln(y_{nk})
Perceptron Error Function (Loss over misclassified patterns) E_P(w) = - sum_{n in M} w^T * (phi_n * t_n)
Mallow's C_p Statistic Formula C_p = (1 / N) * (RSS + 2 * d * sigma_tilde^2)
Akaike Information Criterion (AIC) Formula AIC = -2 * ln(L) + 2 * d
Bayesian Information Criterion (BIC) Formula BIC = -2 * ln(L) + d * ln(N)
Generalization Error Bound for Finite Hypothesis Spaces (Agnostic) L_true(h) <= L_train(h) + sqrt( (ln|H| + ln(2/delta)) / (2*N) )
Generalization Error Bound for Infinite Hypothesis Spaces (VC Bound) L_true(h) <= L_train(h) + sqrt( (VC(H) * (ln(2*N / VC(H)) + 1) + ln(4/delta)) / N )
PAC Learning Sample Complexity Bound (Finite Space, Agnostic) N >= (1 / (2 * epsilon^2)) * ( ln|H| + ln(2 / delta) )
VC Dimension Sample Complexity Bound N >= (1 / epsilon) * ( 4 * log2(2/delta) + 8 * VC(H) * log2(13/epsilon) )
Dual Representation of Linear Regression (Dual Weight Vector) w = X^T * a where a = (I * sigma^2 + X * X^T)^-1 * t
Gram Matrix (Kernel Matrix) Element Definition K_nm = k(x_n, x_m) = phi(x_n)^T * phi(x_m)
Soft-Margin Support Vector Machine (SVM) Primal Objective min_{w, b, xi} (1/2)||w||^2 + C * sum_{i=1}^N xi_i
Soft-Margin SVM Constraints t_i * (w^T * x_i + b) >= 1 - xi_i and xi_i >= 0
Soft-Margin SVM Dual Maximization Objective max_alpha sum(alpha_n) - (1/2) * sum_n sum_m alpha_n * alpha_m * t_n * t_m * k(x_n, x_m)
Soft-Margin SVM Dual Constraints 0 <= alpha_n <= C and sum(alpha_n * t_n) = 0
Gaussian Process Predictive Mean Function m(x_{N+1}) = k^T * C_N^-1 * t
Gaussian Process Predictive Variance Function sigma^2(x_{N+1}) = k(x_{N+1}, x_{N+1}) + sigma^2 - k^T * C_N^-1 * k
State-Value Function V^pi(s) Bellman Expectation Equation V^pi(s) = sum_a pi(a|s) [ R(s,a) + gamma * sum_{s'} P(s'|s,a) * V^pi(s') ]
Action-Value Function Q^pi(s,a) Bellman Expectation Equation Q^pi(s,a) = R(s,a) + gamma * sum_{s'} P(s'|s,a) * sum_{a'} pi(a'|s') * Q^pi(s',a')
Optimal State-Value Function V*(s) Bellman Optimality Equation V*(s) = max_a [ R(s,a) + gamma * sum_{s'} P(s'|s,a) * V*(s') ]
Optimal Action-Value Function Q*(s,a) Bellman Optimality Equation Q*(s,a) = R(s,a) + gamma * sum_{s'} P(s'|s,a) * max_{a'} Q*(s', a')
Value Iteration Value Update Rule V_{k+1}(s) <- max_a [ R(s,a) + gamma * sum_{s'} P(s'|s,a) * V_k(s') ]
Policy Iteration (Greedy Improvement Rule) pi_{k+1}(s) <- argmax_a [ R(s,a) + gamma * sum_{s'} P(s'|s,a) * V^{pi_k}(s') ]
Bellman Optimality Operator T* acting on V (T*V)(s) = max_a [ R(s,a) + gamma * sum_{s'} P(s'|s,a) * V(s') ]
Max-Norm Contraction Property of Bellman Operators ||T f_1 - T f_2||_infinity <= gamma * ||f_1 - f_2||_infinity
Temporal Difference Error (TD Error) delta_t delta_t = r_{t+1} + gamma * V(s_{t+1}) - V(s_t)
Temporal Difference TD(0) State-Value Update Rule V(s_t) <- V(s_t) + alpha * (r_{t+1} + gamma * V(s_{t+1}) - V(s_t))
SARSA (On-Policy Control) Action-Value Update Rule Q(s,a) <- Q(s,a) + alpha * (r + gamma * Q(s',a') - Q(s,a))
Q-Learning (Off-Policy Control) Action-Value Update Rule Q(s,a) <- Q(s,a) + alpha * (r + gamma * max_{a'} Q(s',a') - Q(s,a))
Thompson Sampling Parameter Update for Bernoulli Success alpha_i <- alpha_i + 1
Thompson Sampling Parameter Update for Bernoulli Failure beta_i <- beta_i + 1
Incremental Target/Reward Mean Formula Q_{k}(a) <- Q_{k-1}(a) + (1 / k) * (r_k - Q_{k-1}(a))
Created by: Filotì
 

 



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