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8.0 KiB

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"source": [
"import numpy as np\n",
"import surprise # run 'pip install scikit-surprise' to install surprise"
]
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"execution_count": 3,
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"class MatrixFacto(surprise.AlgoBase):\n",
" '''A basic rating prediction algorithm based on matrix factorization.'''\n",
" \n",
" def __init__(self, learning_rate, n_epochs, n_factors):\n",
" \n",
" self.lr = learning_rate # learning rate for SGD\n",
" self.n_epochs = n_epochs # number of iterations of SGD\n",
" self.n_factors = n_factors # number of factors\n",
" \n",
" def fit(self, trainset):\n",
" '''Learn the vectors p_u and q_i with SGD'''\n",
" \n",
" print('Fitting data with SGD...')\n",
" \n",
" # Randomly initialize the user and item factors.\n",
" p = np.random.normal(0, .1, (trainset.n_users, self.n_factors))\n",
" q = np.random.normal(0, .1, (trainset.n_items, self.n_factors))\n",
" \n",
" # SGD procedure\n",
" for _ in range(self.n_epochs):\n",
" for u, i, r_ui in trainset.all_ratings():\n",
" err = r_ui - np.dot(p[u], q[i])\n",
" # Update vectors p_u and q_i\n",
" p[u] += self.lr * err * q[i]\n",
" q[i] += self.lr * err * p[u]\n",
" # Note: in the update of q_i, we should actually use the previous (non-updated) value of p_u.\n",
" # In practice it makes almost no difference.\n",
" \n",
" self.p, self.q = p, q\n",
" self.trainset = trainset\n",
"\n",
" def estimate(self, u, i):\n",
" '''Return the estmimated rating of user u for item i.'''\n",
" \n",
" # return scalar product between p_u and q_i if user and item are known,\n",
" # else return the average of all ratings\n",
" if self.trainset.knows_user(u) and self.trainset.knows_item(i):\n",
" return np.dot(self.p[u], self.q[i])\n",
" else:\n",
" return self.trainset.global_mean"
]
},
{
"cell_type": "code",
"execution_count": 11,
"metadata": {
"collapsed": true
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"outputs": [],
"source": [
"# data loading. We'll use the movielens dataset (https://grouplens.org/datasets/movielens/100k/)\n",
"# it will be downloaded automatically.\n",
"data = surprise.Dataset.load_builtin('ml-100k')\n",
"data.split(2) # split data for 2-folds cross validation"
]
},
{
"cell_type": "code",
"execution_count": 12,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Evaluating RMSE of algorithm MatrixFacto.\n",
"\n",
"------------\n",
"Fold 1\n",
"Fitting data with SGD...\n",
"RMSE: 0.9826\n",
"------------\n",
"Fold 2\n",
"Fitting data with SGD...\n",
"RMSE: 0.9873\n",
"------------\n",
"------------\n",
"Mean RMSE: 0.9849\n",
"------------\n",
"------------\n"
]
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"source": [
"algo = MatrixFacto(learning_rate=.01, n_epochs=10, n_factors=10)\n",
"surprise.evaluate(algo, data, measures=['RMSE'])"
]
},
{
"cell_type": "code",
"execution_count": 13,
"metadata": {},
"outputs": [
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"name": "stdout",
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"text": [
"Evaluating RMSE of algorithm KNNBasic.\n",
"\n",
"------------\n",
"Fold 1\n",
"Computing the msd similarity matrix...\n",
"Done computing similarity matrix.\n",
"RMSE: 1.0101\n",
"------------\n",
"Fold 2\n",
"Computing the msd similarity matrix...\n",
"Done computing similarity matrix.\n",
"RMSE: 0.9982\n",
"------------\n",
"------------\n",
"Mean RMSE: 1.0042\n",
"------------\n",
"------------\n"
]
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"execution_count": 13,
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"source": [
"# try a neighborhood-based algorithm (on the same data)\n",
"algo = surprise.KNNBasic()\n",
"surprise.evaluate(algo, data, measures=['RMSE'])"
]
},
{
"cell_type": "code",
"execution_count": 14,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Evaluating RMSE of algorithm SVD.\n",
"\n",
"------------\n",
"Fold 1\n",
"RMSE: 0.9604\n",
"------------\n",
"Fold 2\n",
"RMSE: 0.9538\n",
"------------\n",
"------------\n",
"Mean RMSE: 0.9571\n",
"------------\n",
"------------\n"
]
},
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" {'rmse': [0.96042083843476056,\n",
" 0.95382688332712151]})"
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},
"execution_count": 14,
"metadata": {},
"output_type": "execute_result"
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],
"source": [
"# try a more sophisticated matrix factorization algorithm (on the same data)\n",
"algo = surprise.SVD()\n",
"surprise.evaluate(algo, data, measures=['RMSE'])"
]
}
],
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