# SVM算法.rar

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• 2019-11-06 10:59
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SVM的分类与预测。带数据的。可直接使用学习。方便入门。
SVM算法.rar
• SVM算法
• concrete_data.mat
2.2KB
• BreastTissue_data.mat
6.6KB
• feixianxingSVM.m
572B
• svmTrain1.m
4.9KB
• svmPredict.m
1.7KB
• SVMtest.m
2.4KB
• xianxingSVM.m
364B

function [model] = svmTrain(X, Y, C, kernelFunction,sigma,tol, max_passes) if ~exist('tol', 'var') || isempty(tol) tol = 1e-3; end if ~exist('max_passes', 'var') || isempty(max_passes) max_passes = 5; end if ~exist('sigma', 'var') || isempty(sigma) sigma = 1; end % Data parameters m = size(X, 1); n = size(X, 2); % Variables alphas = zeros(m, 1); %拉格朗日算子 b = 0; %超平面截距 E = zeros(m, 1); %评价函数 passes = 0; eta = 0; L = 0; H = 0; if strcmp(func2str(kernelFunction), 'linearKernel') % Vectorized computation for the Linear Kernel % This is equivalent to computing the kernel on every pair of examples K = X*X'; % m*m 样本之间的内积 K是对称矩阵 elseif strfind(func2str(kernelFunction), 'gaussianKernel') % Vectorized RBF Kernel % This is equivalent to computing the kernel on every pair of examples X2 = sum(X.^2, 2); %求向量平方和 K = bsxfun(@plus, X2, bsxfun(@plus, X2', - 2 * (X * X'))); % K=kernelFunction(1,0).^K; K = exp(-K/(2*sigma*sigma)); else % Pre-compute the Kernel Matrix % The following can be slow due to the lack of vectorization K = zeros(m); for i = 1:m for j = i:m K(i,j) = kernelFunction(X(i,:)', X(j,:)'); K(j,i) = K(i,j); %the matrix is symmetric对称 end end end % Train fprintf('\nTraining ...'); dots = 12; while passes < max_passes, num_changed_alphas = 0; for i = 1:m, % Calculate Ei = f(x(i)) - y(i) using (2). % E(i) = b + sum (X(i, :) * (repmat(alphas.*Y,1,n).*X)') - Y(i); E(i) = b + sum (alphas.*Y.*K(:,i)) - Y(i); if ((Y(i)*E(i) < -tol && alphas(i) < C) || (Y(i)*E(i) > tol && alphas(i) > 0)), % In practice, there are many heuristics one can use to select % the i and j. In this simplified code, we select them randomly. j = ceil(m * rand()); while j == i, % Make sure i \neq j j = ceil(m * rand()); end % Calculate Ej = f(x(j)) - y(j) using (2). E(j) = b + sum (alphas.*Y.*K(:,j)) - Y(j); % Save old alphas alpha_i_old = alphas(i); alpha_j_old = alphas(j); % Compute L and H by (10) or (11). if (Y(i) == Y(j)), L = max(0, alphas(j) + alphas(i) - C); H = min(C, alphas(j) + alphas(i)); else L = max(0, alphas(j) - alphas(i)); H = min(C, C + alphas(j) - alphas(i)); end if (L == H), % continue to next i. continue; end % Compute eta by (14). eta = 2 * K(i,j) - K(i,i) - K(j,j); if (eta >= 0), % continue to next i. continue; end % Compute and clip new value for alpha j using (12) and (15). alphas(j) = alphas(j) - (Y(j) * (E(i) - E(j))) / eta; % Clip alphas(j) = min (H, alphas(j)); alphas(j) = max (L, alphas(j)); % Check if change in alpha is significant if (abs(alphas(j) - alpha_j_old) < tol), % continue to next i. % replace anyway alphas(j) = alpha_j_old; continue; end % Determine value for alpha i using (16). alphas(i) = alphas(i) + Y(i)*Y(j)*(alpha_j_old - alphas(j)); % Compute b1 and b2 using (17) and (18) respectively. b1 = b - E(i) ... - Y(i) * (alphas(i) - alpha_i_old) * K(i,j)' ... - Y(j) * (alphas(j) - alpha_j_old) * K(i,j)'; b2 = b - E(j) ... - Y(i) * (alphas(i) - alpha_i_old) * K(i,j)' ... - Y(j) * (alphas(j) - alpha_j_old) * K(j,j)'; % Compute b by (19). if (0 < alphas(i) && alphas(i) < C), b = b1; elseif (0 < alphas(j) && alphas(j) < C), b = b2; else b = (b1+b2)/2; end num_changed_alphas = num_changed_alphas + 1; end end if (num_changed_alphas == 0), passes = passes + 1; else passes = 0; end fprintf('.'); dots = dots + 1; if dots > 78 dots = 0; fprintf('\n'); end % if exist('OCTAVE_VERSION') % fflush(stdout); % end end fprintf(' Done! \n\n'); % Save the model idx = alphas > 0; model.idx=idx; model.X= X(idx,:); model.y= Y(idx); model.kernelFunction = kernelFunction; model.sigma=sigma; model.b= b; model.alphas= alphas(idx); model.w = ((alphas.*Y)'*X)'; end

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