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Math Help - Extending a trend line to a certain point

  1. #1
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    Extending a trend line to a certain point

    Hi,

    I have a program which averages out previous points in a form of an Exponential Moving Average. Please see the pic below where the jumpy light blue line is 'smoothed' by the yellow line:
    Extending a trend line to a certain point-linegraph.png

    What I want is the yellow line extending to the left hand side of the chart to come up with a new value at 0 on the X axis like this:
    Extending a trend line to a certain point-linegraph2.png

    Can anyone help with the forumale to produce the ?? figure on the Y axis, based on previous points to the right. This will need to be turned into code and there may be up to 20 previous X,Y points on the graph. I am sure this doesn't matter though as we just want the formula based on previous points?

    Much appreciated if anyone can help?

    Thanks,

    WG
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  2. #2
    MHF Contributor
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    Re: Extending a trend line to a certain point

    Hey willowgal.

    You could either smooth the whole red line to get one red segment, or you could do a simple linear regression on the points of the smoothed line and get the parameters corresponding to B0 and B1 where your line is just y = f(x) = B0 + B1*x.
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  3. #3
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    Re: Extending a trend line to a certain point

    Many thanks chiro :-)
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