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Tricks with Excel?

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  1. Sep 5, 2015 #1
    I should probably be asking Excel's programmers, but I have been lucky in this forum lately; here is what I got going on:

    I have a data table composed of two variables: time and angular velocity of a particle around a centre point.

    Time is just 0.0, 0.1, 0.2 (in seconds) and so on.

    Angular velocity is given once every 0.1 second in Radians/second. The angular velocity generally decreases but there are small spikes going up and down.

    What I want to do is that I want to know when will the particle be in a position where it is on the right of (or 0 degrees in relation to) the centre.

    My calculus is mediocre, but I think what I need to do is to plot the angular velocity over time on a graph, and then add the area under the curve into blocks of 2Ī€, at the edge of each block would be the point in time where the particle is in the desired position, but there isn't a simple function describing the motion of the particle that I can integrate (due to the spikes) and the data set is kind of big, so I am just wondering if there's any way to get those points in time easily.
     
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  3. Sep 5, 2015 #2

    mfb

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    You can keep adding (time difference*angular velocity), which is the rotation angle in each time step, until your sum exceeds 2 pi, 4 pi and so on.
    If you think those spikes are measurement errors, it might be useful to smoothen the distribution in some way (that depends on the data source).
     
  4. Sep 5, 2015 #3
    I could have done that, but that would take way too long, and it feels like it goes against the purpose of having technology.
     
  5. Sep 5, 2015 #4

    mfb

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    What do you mean with "way too long"? Excel does the calculations for you, of course.
     
  6. Sep 5, 2015 #5
    I guess I didn't get what you were saying, so are you telling me that there is a way to make excel add things up and every time it hits a new "threshold" of 2nĪ€ it tells me?
     
  7. Sep 5, 2015 #6

    Nidum

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    Calculate the incremental angular position using a 'do until' loop .

    Test on angular position >= 2 pi .
     
  8. Sep 5, 2015 #7

    mfb

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    Sure. You can add a third column next to your data and add those values up, and a fourth one to check where n*2pi has been exceeded.
     
  9. Sep 5, 2015 #8

    SteamKing

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    Don't look now, but Excel (and the computer to run it) is "technology". "Technology" is no good to anyone if it just sits on the shelf and remains unused ...
     
  10. Sep 5, 2015 #9
    I don't get what you are trying to say or what is the significance of this to my problem.
     
  11. Sep 5, 2015 #10

    SteamKing

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    People smooth data all the time. There's no shame in it, unless you fiddle with the data to make it come to a pre-determined conclusion.
     
  12. Sep 5, 2015 #11
    okay, I see.
     
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