Matlab将多项式的系数设为0

符号运算时有些多项式的系数值接近于0，像这样

fun = 3.5753839759325595498222646101085e-49*x + 1.8367099231598242312011508394098e-40*y - 3.1684752276643959044089436923507e-34 + 555*z + 4*x*y

需要将其直接消掉，化简成这样

fun = 555*z + 4*x*y

解决方法可以这样，使用coeffs函数，具体doc一下。代码如下

clear
clc
syms x y z real
fun = 3.5753839759325595498222646101085e-49*x + 1.8367099231598242312011508394098e-40*y - 3.1684752276643959044089436923507e-34 + 555*z + 4*x*y

[c, f] = coeffs(fun,[x, y, z]);
len = size(c, 2);
for i =1:len
    if (c(i) < 0.0000000001)
        c(i) = 0;
    end
end
fun_new = c*f'

结果