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Considering the following dataset, how do I find the angle when the two lines intersect at time 4. Please not that the two lines don't represent a function, this is just a data set.

Time     Line 1     Line 2 0        20         19.95 1        20.5       20 2        21         20.05 3        20.5       20 4        22         23 5        23         25 

Thanks for the help!

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    Fit either of the datasets to $y=m x +b$. The angle then is given by $|\arctan(m_2) -\arctan(m_1)|$.2011-05-06
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    You can do it with one arctangent evaluation instead of 2. Use the formula for the tangent of the difference of two angles.2011-05-06
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    I am not sure to understand how I could fit the two datasets to y=mx+b. The datasets aren't linear.2011-05-06
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    Could you provide more information on this. Your data set has some variability to it and inferring a best fit curve for the lines is a statistical problem. Just assuming that the line 1 and line 2 are straight lines between Time 3 and Time 4 makes this a simple geometry problem. Which way of looking at the problem most suits the issue you are looking at?2011-05-06
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    Ian, we can consider that line 1 and line 2 are straight lines between Time 3 and Time 4.2011-05-06
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    "we can consider that line 1 and line 2 are straight lines between Time 3 and Time 4" - then I suppose you can *interpolate* instead of *regressing*...2011-05-06

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