Ning Jia, Author at Towards Data Science https://towardsdatascience.com Publish AI, ML & data-science insights to a global community of data professionals. Wed, 05 Mar 2025 12:25:51 +0000 en-US hourly 1 https://wordpress.org/?v=6.8.1 https://towardsdatascience.com/wp-content/uploads/2025/02/cropped-Favicon-32x32.png Ning Jia, Author at Towards Data Science https://towardsdatascience.com 32 32 From Evaluation to Enlightenment: Delving into Out-of-Sample Predictions in Cross-Validation https://towardsdatascience.com/from-evaluation-to-enlightenment-delving-into-out-of-sample-predictions-in-cross-validation-2db0850463c8/ Wed, 28 Jun 2023 15:45:10 +0000 https://towardsdatascience.com/from-evaluation-to-enlightenment-delving-into-out-of-sample-predictions-in-cross-validation-2db0850463c8/ Understanding cross-validation and applying it in practical daily work is a must-have skill for every data scientist. While the primary purpose of cross-validation is to assess model performance and fine-tune hyperparameters, it offers additional outputs that should be noticed. By obtaining and combining predictions for each fold, we can generate model predictions for the entire […]

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]]> Spectral Entropy – An Underestimated Time Series Feature https://towardsdatascience.com/spectral-entropy-an-underestimated-time-series-feature-94e18ae5b958/ Wed, 07 Dec 2022 14:58:58 +0000 https://towardsdatascience.com/spectral-entropy-an-underestimated-time-series-feature-94e18ae5b958/ I show how spectral entropy helped me solve two time series classification problems.

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]]> Why Is This Trending Time Series Stationary? https://towardsdatascience.com/why-is-this-trending-time-series-stationary-f3fb9447336f/ Sat, 05 Nov 2022 03:17:29 +0000 https://towardsdatascience.com/why-is-this-trending-time-series-stationary-f3fb9447336f/ A study of the Augmented Dickey-Fuller (ADF) test from a weird example

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]]> A new application of structural entropy for multivariate time series anomaly detection https://towardsdatascience.com/a-new-application-of-structural-entropy-for-multivariate-time-series-anomaly-detection-1ea890bfef86/ Fri, 14 Oct 2022 14:15:16 +0000 https://towardsdatascience.com/a-new-application-of-structural-entropy-for-multivariate-time-series-anomaly-detection-1ea890bfef86/ I like time series. In this post, I’ll continue exploring multivariate time series and introduce a new approach for detecting one kind of particular anomaly. Again, I still use entropy, a simple and powerful tool. Although it depends on the application, we can generally assume we like our time series to be continuous and varying […]

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]]> Anomaly Detection for Multivariate Time Series with Structural Entropy https://towardsdatascience.com/anomaly-detection-for-multivariate-time-series-with-structural-entropy-63f9c34cb67/ Wed, 14 Sep 2022 16:03:20 +0000 https://towardsdatascience.com/anomaly-detection-for-multivariate-time-series-with-structural-entropy-63f9c34cb67/ How to find time series correlation anomalies with realistic examples

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]]> What are the odds of getting a parking ticket in Toronto? https://towardsdatascience.com/what-are-the-odds-of-getting-a-parking-ticket-in-toronto-1f090dd0c608/ Fri, 15 Jul 2022 01:44:06 +0000 https://towardsdatascience.com/what-are-the-odds-of-getting-a-parking-ticket-in-toronto-1f090dd0c608/ An exploratory data analysis and a simple statistical model

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]]> Anomaly Detection in Univariate Stochastic Time Series with Spectral Entropy https://towardsdatascience.com/anomaly-detection-in-univariate-stochastic-time-series-with-spectral-entropy-834b63ec9343/ Wed, 08 Jun 2022 13:30:17 +0000 https://towardsdatascience.com/anomaly-detection-in-univariate-stochastic-time-series-with-spectral-entropy-834b63ec9343/ One tip to find regular patterns like sine waves from randomness.

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