# Tagged Questions

Clustering is grouping (partitioning) a set of objects so that items in the same group are more similar to each other than to items in different groups, where the notion of similarity may be variously defined.

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### What are some of the existing methods (preferably with implementations) that cluster dynamic brain network data with signed edge weights? [on hold]

I have a dynamic graph data with nodes and edges attributed to each timestep. The problem is to find how many communities are found at each timestep and what is their membership. I have an existing ...
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### How to Plot Silhouette with Sørensen–Dice Similarity Coefficient

How to plot silhouette with Sørensen–Dice similarity coefficient? I already have the cluster result and distance value. clust: 1 1 2 2 2 metric: ...
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### Minimize the sum of distances between a sample and two “centers”

Suppose we have a set of readings $\{X_{i}\}$, each of which is a real number. What I want is to find 2 numbers, $a$ and $b$, such that minimize the sum of distances between each $X_{i}$ and ...
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### Alternative to QDA and LDA on supervised classification

I have to do a supervised classification on a dataset made by 12 variables and 5 groups. The main problem is that my data are not gaussian so, i cannot make the quadratic and linear discriminant ...
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### How to compute low rank factorization of a symmetric matrix?

I was implementing NEO - KMeans which is described in the following paper. NEO- KMeans Clustering Paper talked about low rank factorization of a matrix Z of size $n \times n$ such that \begin{...
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### Introducing weights into spectral clustering

Suppose I have a data set with points $x_i$ and a dissimilarity measure $d_{ij}$ between each pair, as well as a weight $w_{ij}$ that qualifies the quality of this dissimilarity. I have two problems: ...
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### Non-negative tri-matrix factorization

If I would like to factorize a matrix $W$ ($0\leq W\leq 1$) into 3 matrices, like $W = UAU^T$, is this problem solvable or is there any approximate solution? Here, $U$ is binary, $A\geq 0$ and $U^T$ ...
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### How to convert table into a distance function?

Been stumped on this past paper question for a while, it's in the context of clustering and the next part is using single linkage bottom-up hierarchical clustering to form a dendrogram using your ...
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### How to recompute the markov transition matrix given a reduction to the number of states? Clustering from a transistion matrix

I am been puzzled with this one for sometime. Given a transition matrix (as below) for a markov chain of N states; how do we calculate the transition matrix for N-1 states, where we combined stat n1 ...