NO符号运算.ppt

例：使用sym函数直接创建符号矩阵 sym_matrix=sym([1 2 3;a b c;sin(x) cos(y) z]) sym_matrix = [ 1, 2, 3] [ a, b, c] [ sin(x), cos(y), z] * Matlab Language Programming * 符号矩阵的生成 （3）用命令syms()定义矩阵 syms a b c; M1=sym(classical); M2=sym(red); M3=sym(blue); sym_matrix=[a b c;M1 M2 M3] sym_matrix = [ a, b, c] [ classical, red, blue] * Matlab Language Programming * 符号矩阵的生成 （4）把数值矩阵转化成相应的符号矩阵 例： A=[1 2 3;10 20 30;100 200 300] A = 1 2 3 10 20 30 100 200 300 B=sym(A) B = [ 1, 2, 3] [ 10, 20, 30] [ 100, 200, 300] * Matlab Language Programming * 符号矩阵的索引与修改 生成矩阵： A=[1 2 3;10 20 30;100 200 300] A = 1 2 3 10 20 30 100 200 300 B=sym(A) B = [ 1, 2, 3] [ 10, 20, 30] [ 100, 200, 300] * Matlab Language Programming * B(2,2) ans = 20 如何修改？ B(2,2)=50; B B = [ 1, 2, 3] [ 10, 50, 30] [ 100, 200, 300] * Matlab Language Programming * 直接修改 修改 syms a b c; M1=sym(classical); M2=sym(red); M3=sym(blue); sym_matrix=[a b c;M1 M2 M3] sym_matrix = [ a, b, c] [ classical, red, blue] subs(sym_matrix,d,c) ans = [ a, b, d] [ classical, red, blue] * Matlab Language Programming * 调用方式 A1=subs(A,’new’) A1=subs(A,’new’,’old’) 符号矩阵的四则运算 符号矩阵的基本运算符与数值矩阵的运算符是统一的。 （+ - * / \） det(a)行列式 inv(b)逆运算 rank(a)求秩 a^2幂运算 exp(b)数组指数运算 expm(b)矩阵指数运算 * Matlab Language Programming * 例 a=sym([1/x,1/(x+1);1/(x+2),1/(x+3)]) a = [ 1/x, 1/(x + 1)] [ 1/(x + 2), 1/(x + 3)] b=sym([x,1;x+2,0]) b = [ x, 1] [ x + 2, 0] * Matlab Language Programming * b-a ans = [ x - 1/x, 1 - 1/(x + 1)] [ x - 1/(x + 2) + 2, -1/(x + 3)] 例 a=sym([1/x,1/(x+1);1/(x+2),1/(x+3)]) a = [ 1/x, 1/(x + 1)] [ 1/(x + 2), 1/(x + 3)] b=sym([x,1;x+2,0]) b = [ x, 1] [ x + 2, 0] * Matlab Language Programming * a*b ans = [ (x + 2)/(x + 1) + 1, 1/x] [ x/(x + 2) + (x + 2)/(x + 3), 1/(x + 2)] a*b=? 例 已知f=2*x^2+3*x-5