# Thread: Trendline with polynomial fit (2000)

1. ## Trendline with polynomial fit (2000)

If I have x,y data with a blank cell in the y column I sometimes get a straight line fit even when I request a second order polynomial. This depends on the order of the x,y pairs and the value of x. For example,
1
1 1
2 4
3 12
winds up as a straight line where
1 1
2 4
3 12
1
or
4
1 1
2 4
3 12
result in quadratic equations. Please see attachment for these examples and more. Can anyone explain why?

Peter

2. ## Re: Trendline with polynomial fit (2000)

Why do you specify points with x values that overlap others and with empty y values? If you specify points with x values that don't overlap others and with empty y values, you'll just change the scale of the x axis. But overlapping x values confuse Excel.

3. ## Re: Trendline with polynomial fit (2000)

Hans,
Thanks for your reply.
These were just test cases to try to reproduce a real situation.
Regards,
Peter

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