求助，matlab second derivative approximation,导数逼近

splelvis

clear all;
nx=50;
ny=30;
hx=pi/nx;
x=linspace(0,pi,nx+1);
y=linspace(0,pi,ny+1);
x_plus_h=x+hx.*ones(1,nx+1);
x_minus_h=x-hx.*ones(1,nx+1);
for i=1:nx+1
8 a. ~6 J, ~. K4 M; P5 L; n    for j=1:ny+1
2 H! m3 J, R+ R: _) u. A( A        f_xx(j,i)=(f9(x_plus_h(i),y(j))-2*f9+f9(x_minus_h(i),y(j)))./(hx.^2);   %原式f(x+hx,y)-2f(x,y)+f(x-hx,y)./(hx^2)
    end;
end;
[xx,yy]=meshgrid(x,y);
surf(xx,yy,f_xx);
4 p# u* M) g6 \5 z  K/ I9 Xtitle('partial derivative w.r.t.xx')
，

! v6 ^* A% }- ?/ b* S& N7 ]- K另开一个f9文件，
4 v. B  {/ i- A0 N) s. sfunction l=f9(x,y)
l=exp(sin(x-y));


- V3 ^3 S/ k; |+ m- }( P然后出来说错误了，
' L# j  O* N# z' x0 Z2 S??? Input argument "x" is undefined.

& E+ A9 V9 A" Z. L) @# DError in ==> f9 at 2
l=exp(sin(x-y));
1 A1 L8 h: w% m2 ^- H! D0 UError in ==> partial_derivxx at 11
        f_xx(j,i)=(f9(x_plus_h(i),y(j))-2*f9+f9(x_minus_h(i),y(j)))./(hx.^2);
6 d1 j" c: p' a" g: @5 K" j
9 e0 @2 Q/ ?8 X, {* }1 T各位要怎么改才对呢

splelvis

我自己找到了问题，f9应该是 f9(x(i),y(j))

douglas8j

abc~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

splelvis

不好意思，我也觉得自己太粗心了

douglas8j

henhaodeyipianwenzhang~~~~~~~~~~~~~~~`