[Baeoz]

Is there a mathematical way to find when the underlying data of a trendline become positive? I don't mean eyeballing the trendline and saying 'aha! it's above zero!' because it it were below zero, become above zero means that already the positive values have overwhelmed the negative values. What test is there, apart from going through, manually, small brackets of data in excel and summing up the value?
I have investigated some data, and at a certain point it is positive, but it's before the overall data goes positive, that the smaller contributing segments are positive, up to the point that the trend line is wrong, and the positive data is finished when the trend is clearly above zero, and is just affecting the next few segments, keeping them above zero.


Thanks.

[James Marques]

If you know the equation of the trendline, just set the y-axis value equal to zero and solve for the x-axis variable? Maybe I'm not understanding the question.