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Cubic graphs to equation confusion

  1. Aug 26, 2011 #1
    Hi,

    I have a sensor going into a microcontroller via a adc.

    I have worked out the conversion from the adc value into real terms.

    Now the math takes too long in code to run this. and a look up table with 1024 elements will fill my program memory very quickly.

    So I have put the results into excel, and the graph has come up as a "S" shape, Now I believe this is a cubic graph, but my confusion lies that a general google search shows cubic graphs as backwards N shape, where as mine looks to be spun around by 90 degrees.

    So,

    1: is the graph I have, Cubic, or something else?
    2: how can I work out the formula (a^3 + b^2 + c) from points in my graph?

    Thanks
     
  2. jcsd
  3. Aug 26, 2011 #2
    Maybe you should post the print screen of the graph, in order to help us to recognize the type of function. Anyway, I think that Excel has a function to fit your data with a function, if there is the software automatically tells you the coefficents ;)
    A software that does that is LoggerPro, and probably even Matlab can help you.
     
  4. Aug 26, 2011 #3

    Mute

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    Homework Helper

    I think we really should see a picture of your plot, because it sounds like you don't actually have a function, unless you are accidentally plotting the dependent variable on the vertical axis and the independent variable on the horizontal axis, or if your curve is a very 'thin' s. For example, if your curve is "curvy" enough that it fails the vertical line test (a vertical line should only cross your curve at one point), then you don't have a function. However, if you swapped the horizontal and vertical axes by mistake, then you would have a function, because rotating it should make it pass the vertical line test.
     
  5. Aug 27, 2011 #4
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