How can I convert a cell array to complex double?

Hi everyone, I am new using matlab, I did some calculation using sym in order to get a complex matrix, but I need to conver this matrix to a complex double matrix, how can I do that?

gg =

  25×1 cell array

    {'z(2)*2i - z(6)*2i'                        }
    {'z(1)*2i + z(3)*2i - z(7)*2i'              }
    {'z(2)*2i + z(4)*2i - z(8)*2i'              }
    {'z(3)*2i + z(5)*2i - z(9)*2i'              }
    {'z(4)*2i - z(10)*2i'                       }
    {'z(7)*2i - z(1)*2i - z(11)*2i'             }
    {'z(6)*2i - z(2)*2i + z(8)*2i - z(12)*2i'   }
    {'z(7)*2i - z(3)*2i + z(9)*2i - z(13)*2i'   }
    {'z(8)*2i - z(4)*2i + z(10)*2i - z(14)*2i'  }
    {'z(9)*2i - z(5)*2i - z(15)*2i'             }
    {'z(12)*2i - z(6)*2i - z(16)*2i'            }
    {'z(11)*2i - z(7)*2i + z(13)*2i - z(17)*2i' }
    {'z(12)*2i - z(8)*2i + z(14)*2i - z(18)*2i' }
    {'z(13)*2i - z(9)*2i + z(15)*2i - z(19)*2i' }
    {'z(14)*2i - z(10)*2i - z(20)*2i'           }
    {'z(17)*2i - z(11)*2i - z(21)*2i'           }
    {'z(16)*2i - z(12)*2i + z(18)*2i - z(22)*2i'}
    {'z(17)*2i - z(13)*2i + z(19)*2i - z(23)*2i'}
    {'z(18)*2i - z(14)*2i + z(20)*2i - z(24)*2i'}
    {'z(19)*2i - z(15)*2i - z(25)*2i'           }
    {'z(22)*2i - z(16)*2i'                      }
    {'z(21)*2i - z(17)*2i + z(23)*2i'           }
    {'z(22)*2i - z(18)*2i + z(24)*2i'           }
    {'z(23)*2i - z(19)*2i + z(25)*2i'           }
    {'z(24)*2i - z(20)*2i'                      }

I have tried:

   New = cell2mat(gg);

But I get the next error:

   Error using cat
Dimensions of matrices being concatenated are not consistent.

Error in cell2mat (line 83)
            m{n} = cat(1,c{:,n});

Also I have tried:

   New = str2double(gg);

But I get:

   Nan

I would really appreciate your help. Thank you in advance.

[Stephen23]

What is z ?

[Luis Morales]

Hi Stephen, is a variable, every row is a ODE. So I want to solve a system with 25 ODE and 25 variables. I want to use it for the ode45 solver, something like:

time = linspace(1,10,500);
ini=zeros(1,(5)^2);
[T1,Z1] = ode45(@(t,z) gg(t,z),time,ini);

[Star Strider]

In your Symbolic Math Toolbox calculations, use the vpa function to resolve the problem of whatever ‘gg’ is, for esample:

gg_v = vpa(gg)

If you want to produce a function that the MATLAB numerical ODE solvers can use as an ODE function argument, see the documentation on the odeToVectorField and matlabFunction functions.

[Luis Morales]

Thank you Star, I will check it.

Answer 1

[Walter Roberson]

In modern MATLAB (R2017b or later),

altered_gg = regexprep(gg, '\((\d+)\)', '$1');
as_sym = str2sym(altered_gg);
z_vars = symvar(as_sym);
GG = matlabFunction(as_sym, 'Vars', {z_vars(:)});

then

[T1, Z1] = ode45(GG, time, ini);

[Luis Morales]

Hi Walter Roberson, thank you for your reply. Doing this I got:

Error: Too many input arguments.

Error in odearguments (line 90)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Do I have to do something else?

Thank you again!