各位朋友，在gauss中如何求偏导数？

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各位朋友，在gauss中如何求偏导数？谢谢！

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关键词：GAUSS USS Aus 偏导数 朋友 GAUSS 导数

zhangtao 发表于 2011-2-19 11:58
各位朋友，在gauss中如何求偏导数？谢谢！

gradp 不行么？

Gradp 的官方解释是：Computes first derivative of a function.
所以用这个命令只能求一阶导数，那如何求一阶和二阶偏导数？

gradp

Purpose

Computes the gradient vector or matrix (Jacobian) of a vector-valued function that has been defined in a procedure. Single-sided (forward difference) gradients are computed.

Format

g = gradp(&f,x0);

Input


&f
a pointer to a vector-valued function (f:Kx1 - > Nx1) defined as a procedure. It is acceptable for f(x) to have been defined in terms of global arguments in addition to x, and thus f can return an Nx1 vector:


  
proc f(x);


  
  
retp( exp(x.*b) );


  
endp;

x0
Kx1 vector of points at which to compute gradient.


Output


g
NxK matrix containing the gradients of f with respect to the variable x at x0.


Remarks

gradp will return a row for every row that is returned by f. For instance, if f returns a scalar result, then gradp will return a 1xK row vector. This allows the same function to be used regardless of N, where N is the number of rows in the result returned by f. Thus, for instance, gradp can be used to compute the Jacobian matrix of a set of equations.

Example

proc myfunc(x);

retp( x.*2 .* exp( x.*x./3 ) );

endp;



x0 = 2.5|3.0|3.5;

y = gradp(&myfunc,x0);

  


It is a 3x3 matrix because we are passing it 3 arguments and myfunc returns 3 results when we do that; the off-diagonals are zeros because the cross-derivatives of 3 arguments are 0.

proc myfunc(x)；

retp(x.*2.*exp(x.*x./3));

endp;



x0= 2.5|3.0|3.5;

y=gradp(&myfunc,x0);

运行以上例子，怎么会提示以下错误？谢谢！
(0) : error G0008 : '； retp(x.*2.*exp(x.*x./3))' : Syntax error

>> y;

       82.989017       0.00000000       0.00000000
      0.00000000        281.19753       0.00000000
      0.00000000       0.00000000        1087.9541

这是我的运行结果，没出现错误呀……

proc myfunc(x)；

retp(x.*2.*exp(x.*x./3));

endp;

x0= 2.5|3.0|3.5;

y=gradp(&myfunc,x0);

print y;
还是提示以下错误：


(0) : error G0008 : '； retp(x.*2.*exp(x.*x./3))' : Syntax error

问题还是没有解决，如何在Gauss中求偏导数呢？

近来明白了2楼朋友的说法是正确的，感谢！