Is it possible to rewrite these equation set to matrix form?

1 次查看(过去 30 天)
I am dealing with some equation set to calculate coefficients b. The equation set is as below. The x y z are the inputs. b is output.
syms x [4 1]
syms y [4 1]
syms z [4 1]
b = zeros(4,1);
b(1) = y3*z2 - y2*z3 + y2*z4 - y4*z2 - y3*z4 + y4*z3;
b(2) = y1*z3 - y3*z1 - y1*z4 + y4*z1 + y3*z4 - y4*z3;
b(3) = y2*z1 - y1*z2 + y1*z4 - y4*z1 - y2*z4 + y4*z2;
b(4) = y1*z2 - y2*z1 - y1*z3 + y3*z1 + y2*z3 - y3*z2;
The equation set would be calculation many times. It takes long time. I want to speed it up. I would like to rewrite this equation set into matrix multiplication, like b = A*[x,y,z] . So I could calculate the vector b in one time , not 4 times. Is it possible? I think this may need some math mind, I have not figure it out. Please help me.
I also try to use subs function. But it is very slow.

采纳的回答

Ameer Hamza
Ameer Hamza 2020-6-26
These variables are nonlinearly related, so not sure how do you want to write in matrix form. Also, it is unlikely that it will cause a significant improvement in speed. You are using a symbolic toolbox that is inherently slow as compared to finite-precision floating-point maths. If you know the values of x, y, and z and want to find values of b, then I suggest you use regular MATLAB operators. For example
syms x [4 1]
syms y [4 1]
syms z [4 1]
b = sym(zeros(4,1));
b(1) = y3*z2 - y2*z3 + y2*z4 - y4*z2 - y3*z4 + y4*z3;
b(2) = y1*z3 - y3*z1 - y1*z4 + y4*z1 + y3*z4 - y4*z3;
b(3) = y2*z1 - y1*z2 + y1*z4 - y4*z1 - y2*z4 + y4*z2;
b(4) = y1*z2 - y2*z1 - y1*z3 + y3*z1 + y2*z3 - y3*z2;
b_fun = matlabFunction(b, 'Vars', {[x1 x2 x3 x4], [y1 y2 y3 y4], [z1 z2 z3 z4]});
x_vec = rand(1,4);
y_vec = rand(1,4);
z_vec = rand(1,4);
b_val = b_fun(x_vec, y_vec, z_vec)

更多回答(0 个)

类别

Help CenterFile Exchange 中查找有关 Symbolic Math Toolbox 的更多信息

产品


版本

R2019a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by