Spline function to detect zero crossing

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Melitta 2014-3-21

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https://ww2.mathworks.cn/matlabcentral/answers/122587-spline-function-to-detect-zero-crossing

编辑： Star Strider 2014-3-25

C756.txt

Hi All,

I was hoping someone might be able to help me, I am not very good with Matlab so I apologise if this is a stupid question.

I have a series of data that changes over time from being negative to positive. I would like to detect the point at which the data crosses zero. I believe the best way to do this is using a spline curve but I am not sure how to write the routine. Can anyone help me please?!

Thanks

Mel

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回答（2 个）

Star Strider 2014-3-21

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Not a spline, but my answer to Fast zero-crossings with interpolation seems to work reasonably well. I can probably modify it to work with your data, but I have to know what your data are.

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Melitta 2014-3-25

What does V represent in the above function? Sadly this is as clean and continuous as physiological data get!

Thank you for your help

Star Strider 2014-3-25

编辑：Star Strider 2014-3-25

I labeled your data as matrix V after eliminating all the ‘DIV/0!’ entries, and the last couple lines that didn’t make sense to me. I should have explained that.

I have a robust background in physiology and physiological measurement from both basic science and clinical perspectives, so I did my best to make sense of your data. Unfortunately, I couldn’t. I didn’t see any obvious relationship.

I assume VO2 is oxygen consumption, and Hb is haemoglobin, but I’m not sure what HHb and HHb.VO2 are. If HHb.VO2 is (HHb x VO2), I strongly suggest you not regress it against VO2, since it’s correlated with VO2 by the way you have defined it. The results will be meaningless.

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