Spatio-temporal clustering is a process of grouping objects based on their spatial and temporal similarity. As a consequence, different types and large amounts of spatio-temporal data became available that introduce new challenges to data analysis and require novel approaches to knowledge discovery.
In this chapter we concentrate on the spatio-temporal clustering in geographic space. First, we provide a classification of different types of spatio-temporal data. Then, we focus on one type of spatio-temporal clustering - trajectory clustering, provide an overview of the state-of-the-art approaches and methods of spatio-temporal clustering and finally present several scenarios in different application domains such as movement, cellular networks and environmental studies.
Unable to display preview. Download preview PDF. Skip to main content. Advertisement Hide. Chapter First Online: 07 July This process is experimental and the keywords may be updated as the learning algorithm improves. This is a preview of subscription content, log in to check access. Andrienko G, Andrienko N Spatio-temporal aggregation for visual analysis of movements. Andrienko G, Andrienko N Interactive cluster analysis of diverse types of spatiotemporal data.
Andrienko G, Andrienko N Spatial generalization and aggregation of massive movement data. Andrienko N, Andrienko G Exploratory analysis of spatial and temporal data: a systematic approach.
Spatio-temporal clustering ?
Springer Verlag Google Scholar. Advances in knowledge discovery and data mining pp — Google Scholar. Birant D, Kut A An algorithm to discover spatialtemporal distributions of physical seawater characteristics and a case study in turkish seas. Cohen S. CrossRef Google Scholar. Springer Google Scholar. Gaffney S, Smyth P Trajectory clustering with mixtures of regression models. Gudmundsson J, van KreveldM Computing longest duration flocks in trajectory data. Iyengar VS On detecting space-time clusters.DBSCAN Density-Based Spatial Clustering of Applications with Noise is a data clustering algorithm It is a density-based clustering algorithm because it finds a number of clusters starting from the estimated density distribution of corresponding nodes.
Then, a new unvisited point is retrieved and processed, leading to the discovery of a further cluster or noise. If a point is found to be part of a cluster, its epsilon-neighborhood is also part of that cluster. Blue dots are actual data, red are noise and yellow are discovered clusters. This site uses Akismet to reduce spam.
Learn how your comment data is processed. It starts with an arbitrary starting point that has not been visited. Dataset is a mxn matrix, m is number of item and n is the dimension of data. Neighbors merge with PointNeighbors. Generating some data with normal distribution at.
Adding some noise with uniform distribution. X between [-3,17]. Y between [-3,17]. Most reacted comment. Hottest comment thread. Recent comment authors. Notify of.With Software Carpentry lessons and Data Carpentry lessons you learn the fundamental data skills needed to conduct research in your field and learn to write simple programs.
This one-day workshop will introduce you to Python for analyzing and visualizing spatial-temporal data. We will be using datasets from the environmental sciences that are freely available.Spatial Clustering in Python
Learners need to have some prior knowledge of Python. For instance, what is covered in the Software Carpentry lesson Programming with Python is more than sufficient. Learners must install Python and a few additional python libraries before the class starts. See the setup instructions. Learners must get the metos data before class starts: please download and unzip the file metos-python-data. The actual schedule may vary slightly depending on the topics and exercises chosen by the instructor.
Toggle navigation Home. Schedule Setup Download files and install packages required for the lesson 1. Introduction Where to start? Why using common data formats? Plotting spatio-temporal data with Python How can I create maps with python?
Data analysis with python What is SciPy?
Data analysis with python
How can I use Scipy? Visualize and Publish with Python How to create animation plots and publish them on the web? How to optimize my workflow?
What are xarray and dask? Where to start? Data Formats in Environmental Sciences. What are the most common data formats in Environmental Sciences? What are Coordinate Reference Systems? Plotting spatio-temporal data with Python. How can I create maps with python? What is SciPy? Visualize and Publish with Python. How to create animation plots and publish them on the web?
Handling very large files in Python.Please cite us if you use the software. Clustering of unlabeled data can be performed with the module sklearn. Each clustering algorithm comes in two variants: a class, that implements the fit method to learn the clusters on train data, and a function, that, given train data, returns an array of integer labels corresponding to the different clusters.
One important thing to note is that the algorithms implemented in this module can take different kinds of matrix as input.
These can be obtained from the classes in the sklearn. These can be obtained from the functions in the sklearn. Affinity propagation. Spectral clustering. Ward hierarchical clustering. Agglomerative clustering.
Gaussian mixtures. Non-flat geometry clustering is useful when the clusters have a specific shape, i. This case arises in the two top rows of the figure above. Gaussian mixture models, useful for clustering, are described in another chapter of the documentation dedicated to mixture models. KMeans can be seen as a special case of Gaussian mixture model with equal covariance per component.
The KMeans algorithm clusters data by trying to separate samples in n groups of equal variance, minimizing a criterion known as the inertia or within-cluster sum-of-squares see below. This algorithm requires the number of clusters to be specified. It scales well to large number of samples and has been used across a large range of application areas in many different fields.
The K-means algorithm aims to choose centroids that minimise the inertiaor within-cluster sum-of-squares criterion :. Inertia can be recognized as a measure of how internally coherent clusters are. It suffers from various drawbacks:. Inertia makes the assumption that clusters are convex and isotropic, which is not always the case. It responds poorly to elongated clusters, or manifolds with irregular shapes. Inertia is not a normalized metric: we just know that lower values are better and zero is optimal.
Running a dimensionality reduction algorithm such as Principal component analysis PCA prior to k-means clustering can alleviate this problem and speed up the computations. In basic terms, the algorithm has three steps.
After initialization, K-means consists of looping between the two other steps. The first step assigns each sample to its nearest centroid. The second step creates new centroids by taking the mean value of all of the samples assigned to each previous centroid. The difference between the old and the new centroids are computed and the algorithm repeats these last two steps until this value is less than a threshold.
In other words, it repeats until the centroids do not move significantly. K-means is equivalent to the expectation-maximization algorithm with a small, all-equal, diagonal covariance matrix. The algorithm can also be understood through the concept of Voronoi diagrams. First the Voronoi diagram of the points is calculated using the current centroids. Each segment in the Voronoi diagram becomes a separate cluster.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.
If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. For more information, see the paper:. This algorithm does not require the number of clusters, this value is identified based on the quantity of highly density connected components. The required parameters are the radius and the minimum number of neighbors.
From these parameters, clusters with different formats and the same density, are found [Sander et al. This algorithm can be applied in several contexts in which the identification of densely connected components is desired e. In all these contexts, clusters are identified considering spatial characteristics of the elements.
In this context, many efforts have been made to identify traffic congestion using clustering algorithms. In the other way, [Liu et al.
They defend that vehicle speed can be predicted through its accumulation. Finally, a deep learning method, called Restricted Boltzmann Machine, was proposed for predicting traffic conditions from data generated by taxi GPS in order to recommend roads for taxi drivers [Niu et al.
Traffic congestion is a frequent situation in urban centers nowadays. It occurs because the urban infrastructure can not keep up with the growth of the number of vehicles. Thus, it causes many drawbacks, such as stress, delays, and excessive fuel consumption.
This application aims to identify traffic congestions using the geographic position of taxis provided by GPS. We assume that a vehicle speed can be estimated by its position in different times. Thus, we applied a density clustering algorithm, which takes into account both spatial and non-spatial aspects [R3], to identify traffic congestions from taxi positions.Learn about SciPy for spatio-temporal data analysis.
SciPy is a Python-based ecosystem of open-source software for mathematics, science, and engineering. In particular, these are some of the core packages:. You know some of these packages, for instance NumPy and Matplotlib ; we have used them in previous chapters.
We also use partly IPython when using jupyter notebooks. The Pandas library provides data structures, produces high quality plots with matplotlib and integrates nicely with other libraries that use NumPy arrays. The usage of nose and Sympy are both outside the scope of this lesson. K-means is a widely used method in cluster analysis.
However, this method is valid only if a number of assumptions is valid with your dataset:. On major decision you have to take when using K-means is to choose the number of clusters a priori.
However, as we will see below, this choice is critical and has a strong influence on the results:. The netCDF file we used can be freely downloaded at here. To save the resulting contours, we need to get the coordinates of each point of the contour and create a polygon. Toggle navigation Home. Working with Spatio-temporal data in Python.
Teaching: 0 min Exercises: 0 min.
Questions What is SciPy? How can I use Scipy? Objectives Learn about SciPy for spatio-temporal data analysis Using SciPy clustering algorithms on spatio-temporal data.Data has both a spatial and a temporal context: everything happens someplace and occurs at some point in time. When you consider both the spatial and the temporal context of your data, you can answer questions such as the following: Where are the space-time crime hot spots?
If you are a crime analyst, you might use the results from a space-time Hot Spot Analysis to make sure that your police resources are allocated as effectively as possible.
You want those resources to be in the right places at the right times. Where are the spending anomalies? In an effort to identify fraud, you might use Cluster and Outlier Analysis to scrutinize spending behaviors, looking for outliers in space and time. A sudden change in spending patterns or frequency could suggest suspicious activity.
What are the characteristics of bacteria outbreaks? Suppose you are studying salmonella samples taken from dairy farms in your state. To characterize individual outbreaks, you can run Spatially Constrained Multivariate Clustering on your sample data, constraining cluster membership in both space and time.
Samples close in time and space are most likely to be associated with the same outbreak. Were your decisions or resource allocations effective?
Suppose you wanted to monitor the effectiveness of new policies put in place to decrease drug crimes in your city. You could use Emerging Hot Spots to monitor changes in event data trends such as identifying locations representing new, intensifying, or diminishing hot spots where drug crimes occur. Several tools in the Spatial Statistics toolbox work by assessing each feature within the context of their neighboring features.
When neighbor relationships are defined in terms of both space and time, traditional spatial analyses become space-time analyses. To define neighbor relationships using both spatial and temporal aspects of your data, use the Generate Spatial Weights Matrix tool and select the Space time window option for the Conceptualization of Spatial Relationships parameter.
Similarly, proximal features within 1 kilometer of each other that do not fall within the 7-day time interval of each other will not be considered neighboring features. One common approach to understanding spatial and temporal trends in your data is to break it up into a series of time snapshots.
You might, for example, create separate datasets for week one, week two, week three, week four, and week five. You could then analyze each week separately and present the results of your analysis as either a series of maps or as an animation. While this is an effective way to show trends, how you decide to break up the data is somewhat arbitrary.
If you are analyzing your data week to week, for example, how do you decide where the break falls? Should you break the data between Sunday and Monday? Perhaps Monday through Thursday, and then again Friday through Sunday? And is there something special about analyzing the data in week-long intervals?