How to take gradient of matrix(21X21 dimension) with respect to a vector of(1X8) dimensions?

Question

Nikhil 2015-11-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/254982-how-to-take-gradient-of-matrix-21x21-dimension-with-respect-to-a-vector-of-1x8-dimensions

评论： Walter Roberson 2015-11-16

Hello all,

I have a function which is represented in matrix format with 21X21 components. It depends on 8 design variables and I want to calculate the gradient of this function with respect to these 8 design variables. So can somebody guide on how to calculate gradient of 21X21 matrix with respect to 1X8 dimension vector in Matlab? The expected answer is 21X21X8 dimension matrix. Any help in this matter would be appreciated, Thank you in advance,

Sincerely, Nikhil

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2015-11-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/254982-how-to-take-gradient-of-matrix-21x21-dimension-with-respect-to-a-vector-of-1x8-dimensions#answer_199953

在 MATLAB Online 中打开

vars = symvar(YourMatrix);
for K = length(vars) : -1 : 1
  MatrixGradient(:,:,K) = gradient(YourMatrix, vars(K));
end

2 个评论
显示无隐藏无

Nikhil 2015-11-16

在 MATLAB Online 中打开

Hey, Thank you for your answer! But I tried this approach on simple example. It is giving me an error as follows:

clear all;
vars=symvar('x1 2*(x2)+2;(x1)^2 (x2)^3');
syms x1 x2
M=[x1 2*(x2)+2;(x1)^2 (x2)^3];
for K=length(vars):-1:1
    MatrixGrad(:,:,K)=gradient(M,vars(K));
end

The error that I got is as follows: ??? Undefined function or method 'mtimes' for input arguments of type 'cell'.

Error in ==> gradient>parse_inputs at 130 loc(k) = {h*(1:indx(k))};

Error in ==> gradient at 49 [msg,f,ndim,loc,rflag] = parse_inputs(f,varargin);

Looking forward to your assistance in debugging this error, Thank you again,

Sincerely, Nikhil

Walter Roberson 2015-11-16

在 MATLAB Online 中打开

syms x1 x2
M = [x1 2*(x2)+2;(x1)^2 (x2)^3];
vars = [x1 x2];
for K = length(vars):-1:1
    MatrixGrad(:,:,K) = diff(M,vars(K));
end

请先登录，再进行评论。

Answer 2

Nikhil 2015-11-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/254982-how-to-take-gradient-of-matrix-21x21-dimension-with-respect-to-a-vector-of-1x8-dimensions#answer_199960

在 MATLAB Online 中打开

even following code is giving an error message

vars=symvar([x1 2*(x2)+2;(x1)^2 (x2)^3]);
for K=length(vars):-1:1
    MatrixGrad(:,:,K)=gradient([x1 2*(x2)+2;(x1)^2 (x2)^3],vars(K));
end

error:

??? Error using ==> zeros
Trailing string input must be a valid numeric class name.
Error in ==> gradient at 64
   g  = zeros(size(f),class(f)); % case of singleton dimension

Is it because I am using older version of matlab (r2011) ??