New paper on gait assessment in multiple sclerosis

Check out our newly published research which introduces a semi-supervised clustering method for rotation time series and applies it to successfully group patients diagnosed with multiple sclerosis in terms of similar gait disabilities.

rotation-valued functional data

Department of Mathematics Jean Leray, UMR CNRS 6629


December 13, 2022

Recent approaches in gait analysis involve the use of wearable motion sensors to extract spatio-temporal parameters that characterize multiple aspects of an individual’s gait. In particular, the medical community could largely benefit from this type of devices as they could provide the clinicians with a valuable tool for assessing gait impairment. Motion sensor data are however complex and there is an urgent unmet need to develop sound statistical methods for analyzing such data and extracting clinically relevant information. In this article, we measure gait by following the hip rotation over time and the resulting statistical unit is a time series of unit quaternions. We explore the possibility to form groups of patients with similar walking impairment by taking into account their walking data and their global decease severity with semi-supervised clustering. We generalize a compromise-based method named hclustcompro to unit quaternion time series by combining it with the proper dissimilarity quaternion dynamic time warping. We apply this method on patients diagnosed with multiple sclerosis to form groups of patients with similar walking deficiencies while accounting for the clinical assessment of their overall disability. We also compare the compromise-based clustering approach with the method mergeTrees that falls into a sub-class of ensemble clustering named collaborative clustering. The results provide a first proof of both the interest of using wearable motion sensors for assessing gait impairment and the use of prior knowledge to guide the clustering process. It also demonstrates that compromise-based clustering is a more appropriate approach in this context.

Find out more by reading our paper (Drouin et al. 2022) which can be found at


Drouin, Pierre, Aymeric Stamm, Laurent Chevreuil, Vincent Graillot, Laetitia Barbin, Pierre-Antoine Gourraud, David-Axel Laplaud, and Lise Bellanger. 2022. “Semi-Supervised Clustering of Quaternion Time Series: Application to Gait Analysis in Multiple Sclerosis Using Motion Sensor Data.” Statistics in Medicine.