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. 2017 Feb 14;7(2):e1030. doi: 10.1038/tp.2017.1

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Copyright © 2017 The Author(s)

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/4.0/

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Use/non-use reciprocity parameters. (a) A schematic and the equation used to calculate the root mean square of the successive differences (RMSSD). X(i) is the duration of a use or non-use epoch. There are (n−1) successive differences of use/non-use epochs. (b) A schematic and the equation used to calculate the Similarity Index, Xn(i) refers to the duration of a non-use (red) epoch, Yn(j) refers to the duration of a use (blue) epoch. Each non-use epoch (Xn_i) corresponds to three successive use epochs (Yn_j, Yn_j+1, Yn_j+2). K is the number of non-use epochs in a day. Thus, the similarity index is the average absolute difference between the non-use and use epochs.