关于matlab7.0中，普通矩阵函数funm

MATLAB7中矩阵怎么置0~

可以这样~~~
A(:,:)=0;
就是在不改变矩阵A大小的同时全变为0

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]

funm()确实可以进行矩阵一般函数运算，但这条函数语句在实现过程中使用了一种潜在不稳定的算法，尤其是对于病态矩阵，有可能得出不正确的结果。如果该函数内嵌的检查器检查出不符合计算条件的矩阵，MATLAB就会自动报警。但这个检查器过于灵敏，虚警概率较高。改成log以后，也不是正确的，看第二张图，已经warning 了，就是报警了噻，大致意思就是主矩阵的值可能不正确，或者没有定义啥子的（英语不好，半懂不懂），返回输出的值是次矩阵的值。就是non-principal matrix logarithm is returned.对于常用的矩阵指数和对数运算，建议用专有函数expm()、logm()，这些函数的实现算法与funm()不同。比较好使。</p>

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关于matlab7.0中，普通矩阵函数funm视频