How do I plot a single contour for a 3rd degree polynomial in 2 variables in python?

Asked Oct 06 '18 at 20:33

Active Oct 06 '18 at 20:33

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I have an equation for a surface. It is a polynomial in 2 variables to the 3rd degree. I wrote the following lambda function for it:

def get_poly(w):
    return lambda x1, x2 : w[0] + w[1]*x1 + w[2]*x1 + w[3]*x1**2 + w[4]*x1*x2 + w[5]*x2**2 + w[6]*x1**3 + w[7]*x1**2*x2 + w[8]*x1*x2**2 + w[9]*x2**3

where all w[0]..w[9] are known. I want to plot a single contour of this surface where z = 0. How do I do that? Thank you for your help.

asked Oct 06 '18 at 20:33

deepaktalwardt

It always helps to tell the actual problem. In this case why would `plt.contour(x1,y1,get_poly(w)(x1,y1), [0])` not work? Any error? – ImportanceOfBeingErnest Oct 06 '18 at 21:11
Thanks for the suggestion, but how would you define x1 and y1 (I believe you meant x2) here? – deepaktalwardt Oct 06 '18 at 21:40
Did you read the [contour demo](https://matplotlib.org/gallery/images_contours_and_fields/contour_demo.html)? If there is anything unclear about that, maybe better ask for that first? – ImportanceOfBeingErnest Oct 06 '18 at 21:45

How do I plot a single contour for a 3rd degree polynomial in 2 variables in python?

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