Central difference approximation scripts to calculate first derivatives of smoothed signal got from smooth function, Method: 'Savitzky-Golay'

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SreeHarish Muppirisetty 2014-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/113879-central-difference-approximation-scripts-to-calculate-first-derivatives-of-smoothed-signal-got-from

评论： SreeHarish Muppirisetty 2014-1-27

I want to calculate first derivatives with respect to time for my smoothed data. I used Savitzky-Golay method in 'smooth' matlab function.I need information where I can get:

1. Any downloadable matlab scripts that can do this first derivative calculation by employing central difference approximation.

2. Any matlab function (in-built or user-written that can be downloaded) that can do the same exclusively for this smoothed result using Sgolay method in smooth function. Something like how 'fnder' is to 'csaps'.

Thanks in advance Harish

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Amit 2014-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/113879-central-difference-approximation-scripts-to-calculate-first-derivatives-of-smoothed-signal-got-from#answer_122328

For central difference: http://www.mathworks.com/help/matlab/ref/gradient.html

For SG: http://www.mathworks.com/matlabcentral/fileexchange/30299-savitzky-golay-smoothdifferentiation-filters-and-filter-application

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Amit 2014-1-27

SG is a filter for noisy data. SG fits a pieces of data using polynomials order defined and smooths it. Thus, the derivative of the smoothed data will be in a way differential of those piecewise polynomials. In a way, you can get smoothed data and the derivative at the same time.

SreeHarish Muppirisetty 2014-1-27