MATLAB: Saving values with variables in a matix

matrixsymbolicSymbolic Math Toolboxvariables

Hi all
I not really into Matlab, so ther might some mistakes in my code that are easy to solve.
that is my code so far 
nodes=2
H_d=ones(nodes,nodes)
for N=1:nodes
    for M=1:nodes
        syms omega 
        Pos=sym('pos',[1 nodes]);
        P=sym('p',[1 nodes]);
        
        H_d=(1/2*P(N)^2+omega^2*Pos(M)^
        
        2)
    end
end
My problem is that I want an Matix H_d that is 2×2 large and consists of the values 'calculated' in the for loop.
These are the values created bey the loop, with the variables inside. 
H_d =
 
(omega^2*pos1^2)/2 + p1^2/2
 
 
H_d =
 
(omega^2*pos2^2)/2 + p1^2/2
 
 
H_d =
 
(omega^2*pos1^2)/2 + p2^2/2
 
 
H_d =
 
(omega^2*pos2^2)/2 + p2^2/2
Now I'd like to put all these values in a Matix, like:
H_d=[(omega^2*pos1^2)/2+p1^2/2    (omega^2*pos2^2)/2+p1^2/2
     (omega^2*pos1^2)/2+p2^2/2    (omega^2*pos2^2)/2+p2^2/2]
usually then I had thath problem I just changed H_d to H_d(N,M) and then I get I matrix with all values.
But that didn't work here.
Thats the error Matlab replys:
     The following error occurred converting from sym to double:
Error using symengine (line 58)
DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use VPA.
Error in split_Hamiltonians_diagonalisation (line 16)
        H_d(P(N),Pos(M))=(1/2*(P(N)^2+omega^2*Pos(M)^2));
I am at my wit's end. Hope sopmeone here can help me 🙂

Best Answer

nodes=2;
syms omega 
Pos=sym('pos',[1 nodes]);
P=sym('p',[1 nodes]);       
H_d=sym(ones(nodes,nodes)); % if your creating a square matrix it can also be written as sym(ones(noses)) 
for N=1:nodes
    for M=1:nodes
        H_d(N,M)=(1/2*P(N)^2+omega^2*Pos(M)^2);
    end
end
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