Getting numeric and symbolic coefficients of equation of a straight line in 2d or 3d

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Saikat Banerjee 2020-6-9

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https://ww2.mathworks.cn/matlabcentral/answers/545021-getting-numeric-and-symbolic-coefficients-of-equation-of-a-straight-line-in-2d-or-3d

评论： Ameer Hamza 2020-6-10

Consider the general equation of a straight le in 3d a*x + b*y + c*z + d=0. I would like to get a vector giving [a,b,c,d] including those that are zero or infinity. a,b,c,d can be both numeric and symbolic

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Ameer Hamza 2020-6-9

在 MATLAB Online 中打开

a*x + b*y + c*z + d = 0

is an equation of plane (not line) in 3D. How do you want to find the values of [a,b,c,d]? Do you want to estimate it using curve-fitting?

Saikat Banerjee 2020-6-9

Lets say as an example a equation is given as 7*x - 8*y + d. So my return value or answer is [7,-8,0,c]. I simply want the symbolic/numeric co-efficients of x, y, z, 1. including 0 coefficients

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Ameer Hamza 2020-6-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/545021-getting-numeric-and-symbolic-coefficients-of-equation-of-a-straight-line-in-2d-or-3d#answer_449054

编辑：Ameer Hamza 2020-6-10

在 MATLAB Online 中打开

Try this

syms x y z
f = -9*x + 7*z + 9;
cd = subs(f, [x y z], [0 0 0]);
cx = subs(f, [x y z], [1 0 0])-cd;
cy = subs(f, [x y z], [0 1 0])-cd;
cz = subs(f, [x y z], [0 0 1])-cd;
cd = subs(f, [x y z], [0 0 0]);
c = [cx cy cz cd];