Calculate the gradient of a function

60 次查看（过去 30 天）

显示更早的评论

amine&& 2016-9-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/302968-calculate-the-gradient-of-a-function

回答： garrett batt 2021-8-26

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Hello. I want to calculate the gradient of the function :

g={@(x)-x;@(x)x-1;@(y)-y;@(y)y-1};

with the following command :

gradient(g, [x, y]);

but I get the following error :

Undefined function or variable 'x'.

How I should proceed? Thanks.

2 个评论
显示无隐藏无

John BG 2016-9-13

编辑：John BG 2016-9-13

perhaps you would like to consider proceeding by defining x?

amine&& 2016-9-14

Thanks john, Even if i define the variable that gives me an error. Thanks.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Walter Roberson 2016-9-13

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/302968-calculate-the-gradient-of-a-function#answer_234654

You are confusing the numeric gradient function http://www.mathworks.com/help/matlab/ref/gradient.html with the symbolic gradient function, http://www.mathworks.com/help/symbolic/gradient.html

On the other hand, neither gradient() accepts a vector or cell array of function handles. Numeric gradient() accepts a numeric vector or array, and spacing distances for each of the dimensions. Symbolic gradient() accepts a scalar symbolic expression or symbolic function together with the variables to take the gradient over.

When you have a vector of functions to work with, you almost certainly want a jacobian rather than a gradient. Symbolic jacobian http://www.mathworks.com/help/symbolic/jacobian.html accepts a symbolic expression, symbolic function, or symbolic vector (but not a cell array of function handles.)