# Tag Info

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### Confused about how to apply KMeans on my a dataset with features extracted

For clustering, your data must be indeed integers. Moreover, since k-means is using euclidean distance, having categorical column is not a good idea. Therefore you should also encode the column ...
• 1,669
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### How to measure the similarity between two images?

Check this handout! Well, there a few so... lets go: Given two images $J[x,y]$ and $I[x,y]$ with $(x,y) \in N^{N \times M}$... A - Used in template matching: Template Matching is linear and is not ...
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### How to get the probability of belonging to clusters for k-means?

Let us briefly talk about a probabilistic generalisation of k-means: the Gaussian Mixture Model (GMM). In k-means, you carry out the following procedure: - specify k centroids, initialising their ...
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### Clustering high dimensional data

I don't think any of the clustering techniques "just" work at such scale. The most scalable supposedly is k-means (just do not use Spark/Mahout, they are really bad) and DBSCAN (there are some good ...
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### Clustering for multiple variable

K-means Your data has $7$ dimensions so k-means is worth to try. See the PCA of your data and check if any cluster is visible there as K-means will have a tough time if clusters are not Gaussian. the ...
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### Clustering for mixed numeric and nominal discrete data

Taking a stab: I am trying to identify a clustering technique with a similarity measure that would work for categorical and numeric binary data. Gower Distance is a useful distance metric when the ...

### Clustering geo location coordinates (lat,long pairs)

GPS coordinates can be directly converted to a geohash. Geohash divides the Earth into "buckets" of different size based on the number of digits (short Geohash codes create big areas and longer codes ...
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### K-Means vs hierarchical clustering

I would say hierarchical clustering is usually preferable, as it is both more flexible and has fewer hidden assumptions about the distribution of the underlying data. With k-Means clustering, you ...
• 2,248
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### How to evaluate the K-Modes Clusters?

The are some techniques to choose the number of clusters K. The most common ones are The Elbow Method and The Silhouette Method. Elbow Method In this method, you ...
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### k-means in R, usage of nstart parameter?

nstart option attempts multiple initial configurations and reports on the best one. For example, adding nstart=25 will generate 25 initial random centroids and choose the best one for the algorithm. ...
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### Clustering geo location coordinates (lat,long pairs)

I am probably very late with my answer, but if you are still dealing with geo clustering, you may find this study interesting. It deals with comparison of two fairly different approaches to ...
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### Sklearn: unsupervised knn vs k-means

Unsupervised k-NN Unlike k-means, the unsupervised k-nn does not associate a label to instances. All it can do is tell you what instances in your training data is k-nearest to the point you are ...
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### Accuracy for Kmeans clustering

Accuracy is a measure of comparing the true label to the predicted label. K-Means is an unsupervised clustering algorithm where a predicted label does not exist. So, accuracy can not be directly ...
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### K-Means clustering for mixed numeric and categorical data

You should not use k-means clustering on a dataset containing mixed datatypes. Rather, there are a number of clustering algorithms that can appropriately handle mixed datatypes. Some possibilities ...

### K-Means clustering for mixed numeric and categorical data

It depends on your categorical variable being used. For ordinal variables, say like bad,average and good, it makes sense just to use one variable and have values 0,1,2 and distances make sense here(...
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### K-means incoherent behaviour choosing K with Elbow method, BIC, variance explained and silhouette

Finding the elbow can be made more easier by computing the angles between the consecutive segments. Replace your: kIdx = 10-1 with: ...
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### K-means incoherent behaviour choosing K with Elbow method, BIC, variance explained and silhouette

Just posting a summary of above comments and some more thoughts so that this question is removed from "unanswered questions". Image_doctor's comment is right that these graphs are typical for k-means....

### PCA before K-mean clustering

PCA reduces dimensionality. It does not change the number of observations you have. Nor does it change the order of the data. The n-th observation in your original dataset will still be the n-th ...
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### How to use k-means outputs (extracted features) as SVM inputs?

'Prediction' of k-means algorithm for each observation is just the corresponding centroid. So you can take vector of predicted centroids and use it as a categorical feature (maybe one-hot encoded). ...
• 1,551

### KMeans vs. DBSCAN

In short, KMeans is a distance based clustering technique where depending on the distance between the data points your initialization(usually kmeans++) and clustering works. In kmeans, you initialize ...

### Clustering geo location coordinates (lat,long pairs)

You can use HDBSCAN for this. The python package has support for haversine distance which will properly compute distances between lat/lon points. As the docs mention, you will need to convert your ...
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### Clustering users based on buying behaviour

Big Picture: First of all, the feature set in your data is pretty sparse and uninteresting, so you should not expect to gain much traction from this problem. Use your human mind to think about the ...
• 6,828
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### How to test accuracy of an unsupervised clustering model output?

Since you have the actual labels, you can compare them with the obtained labels and evaluate performance. Typically purity and nmi (normalized mutual information) are used. Read this (Evaluation of ...
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### K-Means clustering - What to do if a cluster has 0 elements?

This is mostly an issue with really bad initialization (random vector generation as well as random labeling are stupid, don't use it - choose k points wth sampling, or k-means++) and with data where k-...

### How to do clustering assuring more than one class per cluster?

This is a very strange design: The goal is to train an ensemble classification model. In general there is no strong reason to use only subsets of the data to train the individual learners, let alone ...
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### How to evaluate distance in k-means clusters?

There are several important points to keep in mind in considering your questions: You should always normalize or standardize your data before applying k-means clustering. This is true of most other ...
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### Categorical data in Kmeans

Converting the categorical data into numerical data isn't really meaningful. Different mappings will give you different solutions. There is an extension of K-means algorithm for categorical data ...
• 502
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### What is the meaning of spherical dataset?

In this case, a picture is a worth a thousand words. They literally mean data whose distribution on X,Y is roughly a sphere. Different clustering algorithms work better on different distributions. For ...
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### calculate distance between each data point of a cluster to their respective cluster centroids

I think this is a more elegant solution. First of all, km.fit_transform() (or km.transform()) gives you back all distances to all clusters. Then you can summarize only the minimum values - which are ...

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