Inuitive example for LSH with toy data

lsh.m

% Inuitive example for LSH with toy data
dimension = 30;
sampleNum = 1000;
hashBitCount = 16;
x = rand(sampleNum, dimension); % data points to hash
w = rand(dimension, hashBitCount); % w vector in hash function
w = w ./ repmat(sqrt(diag(w' * w)'), dimension, 1); % normalization
projection = x * w; % Do the projection
t = median(projection); % empirically provides good result
hashCode = sign(x * w - repmat(t, sampleNum, 1)); % replace x with test data in test phase
% Now we have hash codes as binary vectors in the matrix
compactCode = sum((hashCode + 1) / 2 .* repmat(2 .^ [0:hashBitCount-1], sampleNum, 1), 2); % (hashCode + 1) / 2 maps 1 to 1, -1 to 0.
% Now we have compact hash codes as integers in the vector
% You can also use bi2de if having communication toolbox installed