# Questions tagged [clustering]

Clustering is the problem of finding groups of data points (often modelled as nodes in a graph) that are closer to each other than to other points.

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### What exactly is the difference between supervised and unsupervised learning?

I am trying to understand clustering methods. What I I think I understood: In supervised learning, the categories/labels data is assigned to are known before computation. So, the labels, classes or ...
1answer
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0answers
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### How to map points in high-dimensional space into dense grid in lower-dimensional space?

A formal description of the problem: Given a set $P$ of $n^k$ points in $d$ dimensional space, what algorithm can I use to find a mapping between them and points on a $n \times n \times n...$ grid in ...
0answers
76 views

### Document clustering for summarization

I am curious as to what steps one would reasonably need to take to perform an extraction-based text summarizer. I've taken a look at some papers I've found on Google such as this one, which explains ...
3answers
228 views

### How to calculate IV, EV and optimal k for K-means?

Could someone explain how to calculate the following 3 evaluative properties: Intercluster Variability (IV) - How different are the data points within the same cluster Extracluster Variability (EV) - ...
2answers
144 views

### What happens when you don't use a metric in k-means?

K-means is a clustering algorithm which works like this: ...
2answers
831 views

### Visualize Graph Clusters

I am working on my thesis which involves using ant based techniques for graph clustering. I am testing the algorithm currently and I was wondering if there is a way that I can visualize the clusters ...
1answer
124 views

### What are the (efficient) algorithms to cluster squares into groups using a threshold such that the closest squares form groups?

I have a set of rectangles that needed to be grouped based on their locations. (All the rectangles follow the same orientation.) Two rectangles would be in the same group if the distance between them ...
1answer
195 views

### sum of squared distances from mean equals all-pairs sum of square distances?

In this variance based k-clustering paper they claim that for a cluster with S points: $$|S|\sum_{i \in S}{\|x_i-\bar{x}\|^2} = \sum_{a,b \in S,\ a<b}{\|x_a-x_b\|^2}\,.$$ Why is that? can you ...
1answer
42 views

### Subspace clustering with random transformation

One approach for clustering a high dimensional dataset is to use linear transformation, and the most common approaches are PCA and random projection (where random projection arises from the Johnson-...
1answer
37 views

### k-means clustered data: how to label newly incoming data

I have a data set with labels that were produced by a $k$-means clustering algorithm. Now there is some data (with the same data structure) from another source and I wonder what is the most sensible ...
0answers
38 views

### Algorithms / heuristics for a distributed sorting problem

The setting: There's a cluster of $k$ computers (= nodes). For simplicity, assume their hardware is identical. The network topology can be complicated, but let's simplify and assume it's a clique ...
0answers
31 views

1answer
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### Identify objects (bus) on the map based on coordinates (lat, lon)

Let's say I have an android app that frequently sends current GPS location of the user. If person is driving with bus, I can easily get GPS location of the bus and display it on the map and update it ...
1answer
1k views

### Python: Clustering based on pairwise distance matrix [closed]

I have a matrix which represents the distances between every two relevant items. For example, M[i][j] holds the distance between items i and j. My next aim is to cluster items by these distances. I ...
2answers
348 views

### Keywords for classification of 2D time series data?

Trying to find the right search terms for literature on classifying 2D time series data. I am looking at data from positional tracking of a swarm of insects over time. I have example datasets for ...