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How do I get the gradient at a point on a curved graph?

  1. #1
    utopian_sorceror
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    How do I get the gradient at a point on a curved graph?

    I have a plot of experimental data and I inserted an exponential trendline
    that fits the data very well. I'd like to "differentiate" the curve as I need
    its gradient at certain points; as in I need Excel to draw the tangent to the
    trendline at a given point and tell me its equation. Can anyone help me do
    this?

    Thank you all so much.

  2. #2
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    I don't think Excel knows how to do this as a built in thing. Extract the coefficients of the trendline to a worksheet (using a worksheet function such as LOGEST or a utility that will extract trendline coefficients to a worksheet). Then you can use the coefficients and your knowledge of calculus to determine a formula for the slope of the function at any point. Then use that formula to put together a series of data points that you can plot as the tangent of the curve.

  3. #3
    utopian_sorceror
    Guest

    Re: How do I get the gradient at a point on a curved graph?

    thanks loads, i'll try it out

    "MrShorty" wrote:

    >
    > I don't think Excel knows how to do this as a built in thing. Extract
    > the coefficients of the trendline to a worksheet (using a worksheet
    > function such as LOGEST or a utility that will extract trendline
    > coefficients to a worksheet). Then you can use the coefficients and
    > your knowledge of calculus to determine a formula for the slope of the
    > function at any point. Then use that formula to put together a series
    > of data points that you can plot as the tangent of the curve.
    >
    >
    > --
    > MrShorty
    > ------------------------------------------------------------------------
    > MrShorty's Profile: http://www.excelforum.com/member.php...o&userid=22181
    > View this thread: http://www.excelforum.com/showthread...hreadid=468456
    >
    >


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