# Calculator a Parabola Curve

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It is possible that the control I require is outside of a Parabola, since if I adjust the degree as seen in the image; only the left side of the curve is modified ?

As no matter how much I change the degree, the right side of the curve remains the same that is unless there is another way.

Edited by CinnamonMetal

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set i@id = 1 for all points (set_id_example - node) and move the end-points of curve 2 along the x-axis.

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With a Parabola curve, is there any way to adjust the focus point, the focus point being; the lowest arc in the curve ?

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The focus is determined by the parameters of the parabola

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How do I know where the focus is, when filtering out only points with an id=1, since there are many points with an id=1 ?

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You can define which points are filtered out.  You will get different results with different ids.  You know how to calculate the focus? As hint: If your parabola is y = a*x^2 + b*x + c the derivative is y' = 2*a*x + b. What will happen, if the derivative is 0 (base) and 1 (reflection at this point is from vertical to horizontal (45°)).

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I sorta see what you mean; but how do I define which points are filtered out; which will result in different ids ?

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This is just an option/example (related to your first picutre). If you don't want to use all points you can filter by id. By default you can use all but usually a curve with degree 2 won't fit good (higher degree has better chance for better fit). If you know you have a specific subset of points you want to use , you can set the id for this subset to 1.

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Currently the id=1, although using all the points on the curve won't fit well, I understand; but then you mention, I can use a specific subset of points that I want to use and set the id for that subset to 1 (id=1); although the id is already set to an id=1 ?

In using a subset, I can set the focus point although still maintain control of the curve if I don't use a subset; as it is currently ?

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Your subset should have id = 1 and the other points id != 1 (-1 for example). As I've mentioned before, this is just an example. You can rename this attribute if you want, but make sure to do this in python node aswell. With this method the parameters depends only on the least square fit (so the focus does).

Edited by Aizatulin

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