poly fit warning when drawing vertical curves

Im trying to draw quadratic curves using polyfit function on points that is almost vertical to illustrate a particular shape. eg across points (0,0) (1,5) (0,5) Obviously it would generate warning for having 2 identical x coordinates, is there any alternative I can use to avoid the warning without changing the coordinates of the points? Or is there other functions available to do that?

Thanks

Answer 1

[Walter Roberson]

No. If you have duplicate x coordinates then that is not a polynomial curve. It might be a rotation of a polynomial but not a polynomial.

[Jonathan To]

If i were to do a rotation of a polynomial function, how can i achieve it? The polynomial is intended to be part of a for loop. How can I tell the program to do a rotation instead if a warning pops up?

[Walter Roberson]

Exchange your x and y coordinates, fit that, polyval(), exchange back

[Jonathan To]

I have plot a quadratic using exchanged x and y coordinates, now what code can i use to reflect the curve along y=x?