Refactor

recommender.tex

@@ -29,7 +29,7 @@ In the following, the four most classical \textit{matrix-factorization} approach
 The first and easiest way to solve \textit{matrix-factorization} is to connect the \textit{feature vectors} of the \textit{users} and the \textit{items} using the \textit{inner product}. The result is the \textit{user-item interaction}. In addition, the \textit{error} should be as small as possible. Therefore, $min_{p_u, q_i}{\sum_{(u,i) \in \mathcal{B}} (r_{ui} - \hat{r}_{ui})^{2}}$  is defined as an associated \textit{minimization problem} \citep{Kor09}.
 
 \subsubsection{Regulated Matrix-Factorization}\label{subsec:rmf}
-This problem extends the \textit{basic matrix-factorization} by a \textit{regulation factor} $\lambda$ in the corresponding \textit{minimization problem}. Since $\mathcal{R}$ is thinly occupied, the effect of \textit{overfitting} may occur due to learning from the few known values. The problem with \textit{overfitting} is that the generated \textit{ratings} are too tight. To counteract this, the magnitudes of the previous vectors is taken into account. High magnitudes are punished by a factor $\lambda(\lVert q_i \rVert^2 + \lVert p_u \lVert^2)$ in the \textit{minimization problem}. Overall, the \textit{minimization problem} $min_{p_u, q_i}{\sum_{(u,i) \in \mathcal{B}} (r_{ui} - \hat{r}_{ui})^{2}} + \lambda(\lVert q_i \lVert^2 + \lVert p_u \lVert^2)$ is to be solved.
+This problem extends the \textit{basic matrix-factorization} by a \textit{regulation factor} $\lambda$ in the corresponding \textit{minimization problem}. Since $\mathcal{R}$ is thinly occupied, the effect of \textit{overfitting} may occur due to learning from the few known values. The problem with \textit{overfitting} is that the generated \textit{ratings} are too tight. To counteract this, the magnitudes of the previous vectors are taken into account. High magnitudes are punished by a factor $\lambda(\lVert q_i \rVert^2 + \lVert p_u \lVert^2)$ in the \textit{minimization problem}. Overall, the \textit{minimization problem} $min_{p_u, q_i}{\sum_{(u,i) \in \mathcal{B}} (r_{ui} - \hat{r}_{ui})^{2}} + \lambda(\lVert q_i \lVert^2 + \lVert p_u \lVert^2)$ is to be solved.
 The idea is that especially large entries in $q_i$ or $p_u$ cause $\lVert q_i \rVert, \lVert p_u \rVert$ to become larger. Accordingly, $\lVert q_i \rVert$ and $\lVert p_u \rVert$ increases the larger its entries become. This value is then additionally punished by squaring it. Small values are rewarded and large values are penalized. Additionally the influence of this value can be regulated by $\lambda$ \citep{Kor09}.
 
 \subsubsection{Weighted Regulated Matrix-Factorization}