Keep getting the following error : Unable to convert expression containing symbolic variables into double array.

Other fixes I've seen before do not seem to work on my code and I am unsure as to why this is. The code is the following:

b = [0 -2 -1 -1]'; 
A = [1 0 -1 3; 0 2 1 0; -1 1 6 -1; 3 0 -1 10];
syms alpha real;
x = zeros(4,10);
x(:,1) = [0 1 0 0];
xupdated = zeros(4,10);
a = alpha;

     for i = 1:1:10
        gradient= A*[x(:,i)] + b;
        xupdated(:,i) = x(:,i)-gradient(:,i).*a;
        fupdated = ([xupdated(:,1)]'*A*[xupdated(:,1)]+ [b]'*[xupdated(:,1)]);
        diff_fupdated = diff(fupdated,a);
        S = solve(diff_fupdated,a);
        xupdated = x(:,1) - S*gradient;
        x(:,i+1) = xupdated; 
     end
     
     

Any help would be greatly appreciated.

Answer 1

[Walter Roberson]

Recheck your assignments and your indexing.

b = [0 -2 -1 -1]'; 
A = [1 0 -1 3; 0 2 1 0; -1 1 6 -1; 3 0 -1 10];
syms alpha real;
x = zeros(4,10);
x(:,1) = [0 1 0 0];
xupdated = zeros(4,10, 'sym');
a = alpha;

     for i = 1:1:10
        gradient(:,i) = A*[x(:,i)] + b
        xupdated(:,i) = x(:,i)-gradient(:,i).*a
        fupdated = ([xupdated(:,1)]'*A*[xupdated(:,1)]+ [b]'*[xupdated(:,1)])
        diff_fupdated = diff(fupdated,a)
        S = solve(diff_fupdated,a)
        xupdated(:,i) = x(:,1) - S*gradient(:,i)
        x(:,i+1) = xupdated(:,i)
     end

gradient = 4×1

0 0 0 -1

xupdated = 

fupdated = 

diff_fupdated = 

S = 

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×2

0 0.1500 0 0 0 -0.0500 -1.0000 -0.5000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×3

0 0.1500 0 0 0 0 0 -0.0500 0 -1.0000 -0.5000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×4

0 0.1500 0 0 0 0 0 0 0 -0.0500 0 0 -1.0000 -0.5000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×5

0 0.1500 0 0 0 0 0 0 0 0 0 -0.0500 0 0 0 -1.0000 -0.5000 -1.0000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×6

0 0.1500 0 0 0 0 0 0 0 0 0 0 0 -0.0500 0 0 0 0 -1.0000 -0.5000 -1.0000 -1.0000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×7

0 0.1500 0 0 0 0 0 0 0 0 0 0 0 0 0 -0.0500 0 0 0 0 0 -1.0000 -0.5000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×8

0 0.1500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -0.0500 0 0 0 0 0 0 -1.0000 -0.5000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×9

0 0.1500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -0.0500 0 0 0 0 0 0 0 -1.0000 -0.5000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×10

0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0

gradient = 4×10

0 0.1500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -0.0500 0 0 0 0 0 0 0 0 -1.0000 -0.5000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000

xupdated = 

fupdated = 

diff_fupdated = 

0

S = 

0

xupdated = 

x = 4×11

0 0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0 0

     
     x

x = 4×11

0 0 0 0 0 0 0 0 0 0 0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0 0

[Beehive]

Thanks for the help.