题目

如何将符号函数转换为矩阵函数
例如pdx1=pi*cos(pi*x1) + pi*cos(pi*x1)*cos(pi*x2)
如何将其转换成向量函数?sym2poly只能转换含有单一变量的函数
在线等
一共20积分都送出去了,请别嫌弃

提问时间：2021-02-22

答案

命令就是下面的,coeffs（）
>> syms x1 x2;
>> pdx1=pi*cos(pi*x1) + pi*cos(pi*x1)*cos(pi*x2)
pdx1 =
pi*cos(pi*x1) + pi*cos(pi*x1)*cos(pi*x2)
>> coeffs(pdx1)
ans =
[ 1,1]
>> coeffs(pdx1,x1)
ans =
[pi*cos(pi*x1) + pi*cos(pi*x1)*cos(pi*x2)]
>> coeffs(pdx1,x2)
ans =
[pi*cos(pi*x1) + pi*cos(pi*x1)*cos(pi*x2)]
matlab解释
COEFFS Coefficients of a multivariate polynomial.
C = COEFFS(P) returns the coefficients of the polynomial P with
respect to all the indeterminates of P.
C = COEFFS(P,X) returns the coefficients of the polynomial P with
respect to X.
[C,T] = COEFFS(P,...) also returns an expression sequence of the
terms of P.There is a one-to-one correspondence between the
coefficients and the terms of P.
Examples:
syms x
t = 2 + (3 + 4*log(x))^2 - 5*log(x);
coeffs(expand(t)) = [ 11,19,16]
syms a b c x
y = a + b*sin(x) + c*sin(2*x)
coeffs(y,sin(x)) = [a + c*sin(2*x),b]
coeffs(expand(y),sin(x)) = [a,b + 2*c*cos(x)]
syms x y
z = 3*x^2*y^2 + 5*x*y^3
coeffs(z) = [5,3]
coeffs(z,x) = [5*y^3,3*y^2]
[c,t] = coeffs(z,y) returns c = [5*x,3*x^2],t = [y^3,y^2]