scholarly journals A Fast Screen and Shape Recognition Algorithm for Multiple Change-Point Detection

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Dan Zhuang ◽  
Youbo Liu
Keyword(s):  
Change Point ◽  
Shape Recognition ◽  
Copy Number Variations ◽  
Recognition Algorithm ◽  
Change Point Detection ◽  
Change Points ◽  
Precise Location ◽  
Point Search ◽  
Electrical Distribution Network ◽  
Point Detection

A Fast Screen and Shape Recognition (FSSR) algorithm is proposed with complexity down to O(n) for the multiple change-point detection problems. The proposed FSSR algorithm includes two steps. First, by dividing the data into several subsegments, FSSR algorithm can quickly lock some small subsegments that are likely to contain change-points. Second, through a point by point search in each selected subsegment, FSSR algorithm determines the precise location of the change-point. The simulation study shows that FSSR has obvious speed and stability advantages. Particularly, the sparser the change-points is, the better result will be achieved from FRRS. Finally, we apply FSSR to two real applications to demonstrate its feasibility and robustness. One is the problem of DNA copy number variations identifying; another is the problem of operation scenarios reduction for renewable integrated electrical distribution network.

scholarly journals Change Point Enhanced Anomaly Detection for IoT Time Series Data

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1633
Author(s):  
Elena-Simona Apostol ◽  
Ciprian-Octavian Truică ◽  
Florin Pop ◽  
Christian Esposito
Keyword(s):  
Time Series ◽  
Anomaly Detection ◽  
Change Point ◽  
Time Series Data ◽  
Multivariate Time Series ◽  
Change Point Detection ◽  
Change Points ◽  
Series Data ◽  
Prediction And Forecasting ◽  
Point Detection

Due to the exponential growth of the Internet of Things networks and the massive amount of time series data collected from these networks, it is essential to apply efficient methods for Big Data analysis in order to extract meaningful information and statistics. Anomaly detection is an important part of time series analysis, improving the quality of further analysis, such as prediction and forecasting. Thus, detecting sudden change points with normal behavior and using them to discriminate between abnormal behavior, i.e., outliers, is a crucial step used to minimize the false positive rate and to build accurate machine learning models for prediction and forecasting. In this paper, we propose a rule-based decision system that enhances anomaly detection in multivariate time series using change point detection. Our architecture uses a pipeline that automatically manages to detect real anomalies and remove the false positives introduced by change points. We employ both traditional and deep learning unsupervised algorithms, in total, five anomaly detection and five change point detection algorithms. Additionally, we propose a new confidence metric based on the support for a time series point to be an anomaly and the support for the same point to be a change point. In our experiments, we use a large real-world dataset containing multivariate time series about water consumption collected from smart meters. As an evaluation metric, we use Mean Absolute Error (MAE). The low MAE values show that the algorithms accurately determine anomalies and change points. The experimental results strengthen our assumption that anomaly detection can be improved by determining and removing change points as well as validates the correctness of our proposed rules in real-world scenarios. Furthermore, the proposed rule-based decision support systems enable users to make informed decisions regarding the status of the water distribution network and perform effectively predictive and proactive maintenance.

scholarly journals Locally adaptive change-point detection (LACPD) with applications to environmental changes

2021 ◽  
Author(s):  
Mehdi Moradi ◽  
Manuel Montesino-SanMartin ◽  
M. Dolores Ugarte ◽  
Ana F. Militino
Keyword(s):  
Time Series ◽  
Change Point ◽  
Error Probability ◽  
Type I Error ◽  
Change Point Detection ◽  
Alternative Methods ◽  
Change Points ◽  
Type I ◽  
Type I Error Probability ◽  
Point Detection

AbstractWe propose an adaptive-sliding-window approach (LACPD) for the problem of change-point detection in a set of time-ordered observations. The proposed method is combined with sub-sampling techniques to compensate for the lack of enough data near the time series’ tails. Through a simulation study, we analyse its behaviour in the presence of an early/middle/late change-point in the mean, and compare its performance with some of the frequently used and recently developed change-point detection methods in terms of power, type I error probability, area under the ROC curves (AUC), absolute bias, variance, and root-mean-square error (RMSE). We conclude that LACPD outperforms other methods by maintaining a low type I error probability. Unlike some other methods, the performance of LACPD does not depend on the time index of change-points, and it generally has lower bias than other alternative methods. Moreover, in terms of variance and RMSE, it outperforms other methods when change-points are close to the time series’ tails, whereas it shows a similar (sometimes slightly poorer) performance as other methods when change-points are close to the middle of time series. Finally, we apply our proposal to two sets of real data: the well-known example of annual flow of the Nile river in Awsan, Egypt, from 1871 to 1970, and a novel remote sensing data application consisting of a 34-year time-series of satellite images of the Normalised Difference Vegetation Index in Wadi As-Sirham valley, Saudi Arabia, from 1986 to 2019. We conclude that LACPD shows a good performance in detecting the presence of a change as well as the time and magnitude of change in real conditions.

scholarly journals Change-point detection in wind turbine SCADA data for robust condition monitoring with normal behaviour models

2020 ◽  
Author(s):  
Simon Letzgus
Keyword(s):  
Wind Turbine ◽  
Change Point ◽  
Significant Loss ◽  
Change Point Detection ◽  
Training Data ◽  
Change Points ◽  
Detection Methods ◽  
Full Potential ◽  
Normal Behaviour ◽  
Point Detection

Abstract. Analysis of data from wind turbine supervisory control and data acquisition (SCADA) systems has attracted considerable research interest in recent years. The data is predominantly used to gain insights into turbine condition without the need for additional sensing equipment. Most successful approaches apply semi-supervised anomaly detection methods, also called normal behaivour models, that use clean training data sets to establish healthy component baseline models. However, one of the major challenges when working with wind turbine SCADA data in practice is the presence of systematic changes in signal behaviour induced by malfunctions or maintenance actions. Even though this problem is well described in literature it has not been systematically addressed so far. This contribution is the first to comprehensively analyse the presence of change-points in wind turbine SCADA signals and introduce an algorithm for their automated detection. 600 signals from 33 turbines are analysed over an operational period of more than two years. During this time one third of the signals are affected by change-points. Kernel change-point detection methods have shown promising results in similar settings but their performance strongly depends on the choice of several hyperparameters. This contribution presents a comprehensive comparison between different kernels as well as kernel-bandwidth and regularisation-penalty selection heuristics. Moreover, an appropriate data pre-processing procedure is introduced. The results show that the combination of Laplace kernels with a newly introduced bandwidth and penalty selection heuristic robustly outperforms existing methods. In a signal validation setting more than 90 % of the signals were classified correctly regarding the presence or absence of change-points, resulting in a F1-score of 0.86. For a change-point-free sequence selection the most severe 60 % of all CPs could be automatically removed with a precision of more than 0.96 and therefore without a significant loss of training data. These results indicate that the algorithm can be a meaningful step towards automated SCADA data pre-processing which is key for data driven methods to reach their full potential. The algorithm is open source and its implementation in Python publicly available.

scholarly journals A Remote Sensing-Based Assessment of Water Resources in the Arabian Peninsula

2021 ◽  
Vol 13 (2) ◽  
pp. 247
Author(s):  
Youssef Wehbe ◽  
Marouane Temimi
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Water Resources ◽  
Change Point ◽  
Arabian Peninsula ◽  
Change Point Detection ◽  
Change Points ◽  
Point Detection ◽  
Precipitation Trends

A better understanding of the spatiotemporal distribution of water resources is crucial for the sustainable development of hyper-arid regions. Here, we focus on the Arabian Peninsula (AP) and use remotely sensed data to (i) analyze the local climatology of total water storage (TWS), precipitation, and soil moisture; (ii) characterize their temporal variability and spatial distribution; and (iii) infer recent trends and change points within their time series. Remote sensing data for TWS, precipitation, and soil moisture are obtained from the Gravity Recovery and Climate Experiment (GRACE), the Tropical Rainfall Measuring Mission (TRMM), and the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E), respectively. The study relies on trend analysis, the modified Mann–Kendall test, and change point detection statistics. We first derive 10-year (2002–2011) seasonal averages from each of the datasets and intercompare their spatial organization. In the absence of large-scale in situ data, we then compare trends from GRACE TWS retrievals to in situ groundwater observations locally over the subdomain of the United Arab Emirates (UAE). TWS anomalies vary between −6.2 to 3.2 cm/month and −6.8 to −0.3 cm/month during the winter and summer periods, respectively. Trend analysis shows decreasing precipitation trends (−2.3 × 10−4 mm/day) spatially aligned with decreasing soil moisture trends (−1.5 × 10−4 g/cm3/month) over the southern part of the AP, whereas the highest decreasing TWS trends (−8.6 × 10−2 cm/month) are recorded over areas of excessive groundwater extraction in the northern AP. Interestingly, change point detection reveals increasing precipitation trends pre- and post-change point breaks over the entire AP region. Significant spatial dependencies are observed between TRMM and GRACE change points, particularly over Yemen during 2010, revealing the dominant impact of climatic changes on TWS depletion.

Change Point Detection For Clustered Expression Data In Short Time Series.

2021 ◽  
Author(s):  
Miriam Sieg ◽  
Lina Katrin Sciesielski ◽  
Karin Kirschner ◽  
Jochen Kruppa
Keyword(s):  
Time Series ◽  
Confidence Intervals ◽  
Change Point ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Change Point Detection ◽  
Change Points ◽  
Point Detection ◽  
Over Time ◽  
Time Point

Abstract Background: In longitudinal studies, observations are made over time. Hence, the single observations at each time point are dependent, making them a repeated measurement. In this work, we explore a different, counterintuitive setting: At each developmental time point, a lethal observation is performed on the pregnant or nursing mother. Therefore, the single time points are independent. Furthermore, the observation in the offspring at each time point is correlated with each other because each litter consists of several (genetically linked) littermates. In addition, the observed time series is short from a statistical perspective as animal ethics prevent killing more mother mice than absolutely necessary, and murine development is short anyway. We solve these challenges by using multiple contrast tests and visualizing the change point by the use of confidence intervals.Results: We used linear mixed models to model the variability of the mother. The estimates from the linear mixed model are then used in multiple contrast tests.There are a variety of contrasts and intuitively, we would use the Changepoint method. However, it does not deliver satisfying results. Interestingly, we found two other contrasts, both capable of answering different research questions in change point detection: i) Should a single point with change direction be found, or ii) Should the overall progression be determined? The Sequen contrast answers the first, the McDermott the second. Confidence intervals deliver effect estimates for the strength of the potential change point. Therefore, the scientist can define a biologically relevant limit of change depending on the research question.Conclusion: We present a solution with effect estimates for short independent time series with observations nested at a given time point. Multiple contrast tests produce confidence intervals, which allow determining the position of change points or to visualize the expression course over time. We suggest to use McDermott’s method to determine if there is an overall significant change within the time frame, while Sequen is better in determining specific change points. In addition, we offer a short formula for the estimation of the maximal length of the time series.

A Novel Change-Point Detection Approach for Monitoring High-Dimensional Traffics in Distributed Systems

2014 ◽  
Vol 536-537 ◽  
pp. 499-511 ◽  
Author(s):  
Li Zhao ◽  
Qian Liu ◽  
Peng Du ◽  
Ge Fu ◽  
Wei Cao
Keyword(s):  
Time Series ◽  
Distributed Systems ◽  
Change Point ◽  
Principal Component ◽  
Change Point Detection ◽  
Change Points ◽  
Clustering Methods ◽  
Detection Approach ◽  
Time Series Segmentation ◽  
Point Detection

Change-point detection is the problem of finding abrupt changes in time-series. However, the meaningful changes are usually difficult to identify from the original massive traffics, due to high dimension and strong periodicity. In this paper, we propose a novel change-point detection approach, which simultaneously detects change points from all dimensions of the traffics with three steps. We first reduce the dimensions by the classical Principal Component Analysis (PCA), then we apply an extended time-series segmentation method to detect the nontrivial change times, finally we identify the responsible applications for the changes by F-test. We demonstrate through experiments on datasets collected from four distributed systems with 44 applications that the proposed approach can effectively detect the nontrivial change points from the multivariate and periodical traffics. Our approach is more appropriate for mining the nontrivial changes in traffic data comparing with other clustering methods, such as center-based Kmeans and density-based DBSCAN.

scholarly journals Using Graph Spectral to solve Change Point Detection Problems

2018 ◽  
Author(s):  
Luis Gustavo C. Uzai ◽  
André Y. Kashiwabara
Keyword(s):  
Time Series ◽  
Change Point ◽  
State Of The Art ◽  
The State ◽  
Change Point Detection ◽  
Change Points ◽  
Graph Spectrum ◽  
Point Detection ◽  
Over Time

Time series are sequence of values distributed over time. Analyzing time series is important in many areas including medical, financial, aerospace, commercial and entertainment. Change Point Detection is the problem of identifying changes in meaning or distribution of data in a time series. This article presents Spec, a new algorithm that uses the graph spectrum to detect change points. The Spec was evaluated using the UCR Archive which is a large da- tabase of different time series. Spec performance was compared to the PELT, ECP, EDM, and gSeg algorithms. The results showed that Spec achieved a better accuracy compared to the state of the art in some specific scenarios and as efficient as in most cases evaluated.

CPMAN: Change Point Detection Approach in Time Series Based on the Prediction of Multi-stage Attention Networks

2021 ◽  
Vol 30 (05) ◽  
pp. 2150026
Author(s):  
Haizhou Du ◽  
Ziyi Duan ◽  
Yang Zheng
Keyword(s):  
Time Series ◽  
Change Point ◽  
Early Stage ◽  
Change Point Detection ◽  
Change Points ◽  
Series Data ◽  
Attention Networks ◽  
Multi Stage ◽  
Detection Approach ◽  
Point Detection

Time series change point detection can identify the locations of abrupt points in many dynamic processes. It can help us to find anomaly data in an early stage. At the same time, detecting change points for long, periodic, and multiple input series data has received a lot of attention recently, and is universally applicable in many fields including power, environment, finance, and medicine. However, the performance of classical methods typically scales poorly for such time series. In this paper, we propose CPMAN, a novel prediction-based change point detection approach via multi-stage attention networks. Our model consists of two key modules. First, in the time series prediction module, we employ the multi-stage attention-based networks and integrate the multi-series fusion mechanism. This module can adaptively extract features from the relevant input series and capture the long-term temporal dependencies. Secondly, in the change point detection module, we use the wavelet analysis-based algorithm to detect change points efficiently and identify the change points and outliers. Extensive experiments are conducted on various real-world datasets and synthetic datasets, proving the superiority and effectiveness of CPMAN. Our approach outperforms the state-of-the-art methods by up to 12.1% on the F1 Score.

scholarly journals Prediction of stock switching points by financial news

2021 ◽  
Author(s):  
Saeede Sadat Asadi Kakhki
Keyword(s):  
Change Point ◽  
Latent Dirichlet Allocation ◽  
Performance Metrics ◽  
Change Point Detection ◽  
Change Points ◽  
Detection Methods ◽  
Financial News ◽  
Point Detection ◽  
Stock Change ◽  
Random Guessing

The purpose of this study is to detect stock switching points from historical stock data and analyze corresponding financial news to predict upcoming stock switching points. Various change point detection methods have been investigated in the literature, such as online bayesian change point detection technique. Prediction of stock changing points using financial news has been implemented by different types of text mining techniques. In this study, online bayesian change point detection is implemented to detect stock switching points from historical stock data. Relevant news to detected change points are retrieved in the past and Latent Dirichlet Allocation technique is used to learn the hidden structures in the news data. Unseen news are then transferred to the trained topic representation. Similarity of relevant news and unseen news are used for prediction of future stock change points. Results show that stock switching points can be detected by historical stock data with better performance comparing to random guessing. It is possible to predict stock switching points by only fraction of financial news and with good result in terms of common performance metrics. According to this research, traders can take advantage of financial news to enhance prediction of future stock switching points.

scholarly journals Prediction of stock switching points by financial news

2021 ◽  
Author(s):  
Saeede Sadat Asadi Kakhki
Keyword(s):  
Change Point ◽  
Latent Dirichlet Allocation ◽  
Performance Metrics ◽  
Change Point Detection ◽  
Change Points ◽  
Detection Methods ◽  
Financial News ◽  
Point Detection ◽  
Stock Change ◽  
Random Guessing

The purpose of this study is to detect stock switching points from historical stock data and analyze corresponding financial news to predict upcoming stock switching points. Various change point detection methods have been investigated in the literature, such as online bayesian change point detection technique. Prediction of stock changing points using financial news has been implemented by different types of text mining techniques. In this study, online bayesian change point detection is implemented to detect stock switching points from historical stock data. Relevant news to detected change points are retrieved in the past and Latent Dirichlet Allocation technique is used to learn the hidden structures in the news data. Unseen news are then transferred to the trained topic representation. Similarity of relevant news and unseen news are used for prediction of future stock change points. Results show that stock switching points can be detected by historical stock data with better performance comparing to random guessing. It is possible to predict stock switching points by only fraction of financial news and with good result in terms of common performance metrics. According to this research, traders can take advantage of financial news to enhance prediction of future stock switching points.

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