how to get matlab to differentiate in increments of 1 rather than 0.01

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Ross Hanna
Ross Hanna 2017-9-8
评论： Robert U 2017-9-8
Hi there. I am trying to use forward velocity data from a motorcycle to find the suspension position. When doing this i need the acceleration so i differentiate the data i have using diff() to give the acceleration. When i do this however the answer is a factor of 100 out. When trying to find the cause i noticed that the recording module takes readings every 100th of a second. i get that MATLAB is essentially finding the gradient between my two data points then the next, then the next. My question is, how do i get matlab to find dx/dt in one second increments rather than 100th's of a second? thanks
  2 个评论
José-Luis
José-Luis 2017-9-8
I don't get it.
If you are doing this numerically, a finer gradient would just be a linear interpolation. Am I missing something?
Just resample() your data and calculate the gradient on that.
Robert U
Robert U 2017-9-8
Hi Ross Hanna,
either you take every 100th sample which would result in a loss of information or you have to remember that dx/dt in time discrete systems is approximated by (x(t2)-x(t1))/(t2-t1) where diff(x) is giving you only the x-part of the approximate.
In order to correct the faulty factor 100 you would have to divide diff(x) by the corresponding time steps.
Kind regards,
Robert

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