Error when trying to solve a "Matricial" equation : problem of indices

Hello,

I try to solve a system of equations (actually, this is like a "Matricial equations since I would like that each elements of 2 matrices to be equal)

The 2 matrices to be equal are named :

FISH_GCsp_XC_SYM

and

FISH_GCsp_XC_SYM2

I have just put a crucial constraint in my system, i.e :

% Set 1 bias spectro equal for sp and xc
FISH_GCsp_SYM(8,:) = FISH_XC_SYM(8,:)
FISH_GCsp_SYM(:,8) = FISH_XC_SYM(:,8)

Here is the entire scrit :

FISH_GCsp_SYM = sym('sp_', [8 8])
FISH_XC_SYM = sym('xc_', [8 8])

FISH_GCsp_SYM2 = sym('sp2_', [9 9])
FISH_XC_SYM2 = sym('xc2_', [9 9])

% Set 1 bias spectro equal for sp and xc
FISH_GCsp_SYM(8,:) = FISH_XC_SYM(8,:)
FISH_GCsp_SYM(:,8) = FISH_XC_SYM(:,8)

% Sum for  Fisher matrices;
FISH_GCsp_XC_SYM = FISH_GCsp_SYM + FISH_XC_SYM;

% Marginalisation on 9th dimension
COV_GCsp_SYM2 = inv(FISH_GCsp_SYM2)
COV_XC_SYM2 = inv(FISH_XC_SYM2)
COV_GCsp_SYM2(9,:) = [];
COV_GCsp_SYM2(:,9) = [];
COV_XC_SYM2(9,:) = [];
COV_XC_SYM2(:,9) = [];
FISH_GCsp_SYM2 = inv(COV_GCsp_SYM2);
FISH_XC_SYM2 = inv(COV_XC_SYM2);    
    
% Sum for Fisher matrices;
FISH_GCsp_XC_SYM2 = FISH_GCsp_SYM2 + FISH_XC_SYM2;

% Matricial equality
eqn = FISH_GCsp_XC_SYM == FISH_GCsp_XC_SYM2;

% Solving : matrix1 equal to matrix2
sol = solve([eqn(:)], FISH_GCsp_XC_SYM(:,8))

The unknown to determine symbolicly is the last colum of FISH_GCsp_XC_SYM , i.e FISH_GCsp_XC_SYM(:,8) (so 8 unknown at total).

Unfortunately, I get the following error at execution :

Error using sym.getEqnsVars>checkVariables (line 92)
Second argument must be a vector of symbolic variables.

Error in sym.getEqnsVars (line 54)
    checkVariables(vars);

Error in solve>getEqns (line 429)
[eqns, vars] = sym.getEqnsVars(argv{:});

Error in solve (line 226)
[eqns,vars,options] = getEqns(varargin{:});

Error in building_observable_to_find_SIMPLE_EXAMPLE_ONLY_1_BIAS_COMMON (line 190)
sol = solve([eqn(:)], FISH_GCsp_XC_SYM(:,8))

I don't understand why it fails.

If someone could tell me what's wrong, this would be fine.

Best regards

Answer 1

[Walter Roberson]

replace the loop with just

eqn = FISH_GCsp_XC_SYM == FISH_GCsp_XC_SYM2;

Answer 2

[petit]

@Walter Roberson , Thanks for your quick answer.

I tried like you suggested :

eqn = FISH_GCsp_XC_SYM == FISH_GCsp_XC_SYM2;
% Solving : matrix1 equal to matrix2
sol = solve([eqn(:)], FISH_GCsp_XC_SYM(:,8))

But I get this error :

Error using sym.getEqnsVars>checkVariables (line 92)
Second argument must be a vector of symbolic variables.

Error in sym.getEqnsVars (line 54)
    checkVariables(vars);

Error in solve>getEqns (line 429)
[eqns, vars] = sym.getEqnsVars(argv{:});

Error in solve (line 226)
[eqns,vars,options] = getEqns(varargin{:});

Error in building_observable_to_find_SIMPLE_EXAMPLE_ONLY_1_BIAS_COMMON (line 190)
sol = solve([eqn(:)], FISH_GCsp_XC_SYM(:,8))

What do you think about this error message ? How to circumvent it ?

Regards