Filling symbolic arrays while setting zeros when filling these arrays since useless variables

Hello, below a code snippet to fill the symbolic matrixes FISH_BIG_GCsp and FISH_BIG_XC. Unfortunately, I am not filling entirely these 2 arrays and the execution takes a loo long time since I am taking into account unncessary symbolic values.

The ideal would be to have like I do for numerical arrays, that is to say, set zeros(31,31) and fill after the arrays with assignement : that allows me to not take into account (or at least simplify the execution time) the zeros.

But I don't know how to do the same it with symbolic arrays. If someone could help me, this would be fine

Here below the code snippet :

FISH_SYM = sym('xc_', [31,31], 'positive');
FISH_BIG_GCsp = sym('sp_', [31,31], 'positive');
FISH_BIG_XC = sym('xc_', [31,31], 'positive');

% Block bias spectro + pshot and correlations
FISH_BIG_GCsp(1:7,1:7) = FISH_GCsp_SYM(1:7,1:7)
FISH_BIG_GCsp(7:17,7:17) = FISH_GCsp_SYM(7:17,7:17)
FISH_BIG_GCsp(1:7,7:17) = FISH_GCsp_SYM(1:7,7:17)
FISH_BIG_GCsp(7:17,1:7) = FISH_GCsp_SYM(7:17,1:7)
% Block bias photo and correlations
FISH_BIG_XC(1:7,1:7) = FISH_XC_SYM(1:7,1:7)
FISH_BIG_XC(21:31,21:31) = FISH_XC_SYM(11:21,11:21)
FISH_BIG_XC(1:7,21:31) = FISH_XC_SYM(1:7,11:21)
FISH_BIG_XC(21:31,1:7) = FISH_XC_SYM(11:21,1:7)
% Block I.A and correlations
FISH_BIG_XC(18:20,18:20) = FISH_XC_SYM(8:10,8:10)
FISH_BIG_XC(1:7,18:20) = FISH_XC_SYM(1:7,8:10)
FISH_BIG_XC(18:20,1:7) = FISH_XC_SYM(8:10,1:7)

% Final summation
FISH_SYM = FISH_BIG_GCsp + FISH_BIG_XC

[Walter Roberson]

You mean like

FISH_BIG_XC = zeros(31,31,'sym');

[petit]

@Walter Roberson

Thanks for your quick answer but I can't manage to find the trick. I tried your solution like this :

FISH_SYM = zeros(31,31,'sym');
FISH_BIG_GCsp = zeros(31,31,'sym');
FISH_BIG_XC = zeros(31,31,'sym');

FISH_SYM = sym('xc_', [31,31], 'positive');
FISH_BIG_GCsp = sym('sp_', [31,31], 'positive');
FISH_BIG_XC = sym('xc_', [31,31], 'positive');

% Block bias spectro + pshot and correlations
FISH_BIG_GCsp(1:7,1:7) = FISH_GCsp_SYM(1:7,1:7)
FISH_BIG_GCsp(7:17,7:17) = FISH_GCsp_SYM(7:17,7:17)
FISH_BIG_GCsp(1:7,7:17) = FISH_GCsp_SYM(1:7,7:17)
FISH_BIG_GCsp(7:17,1:7) = FISH_GCsp_SYM(7:17,1:7)
% Block bias photo and correlations
FISH_BIG_XC(1:7,1:7) = FISH_XC_SYM(1:7,1:7)
FISH_BIG_XC(21:31,21:31) = FISH_XC_SYM(11:21,11:21)
FISH_BIG_XC(1:7,21:31) = FISH_XC_SYM(1:7,11:21)
FISH_BIG_XC(21:31,1:7) = FISH_XC_SYM(11:21,1:7)
% Block I.A and correlations
FISH_BIG_XC(18:20,18:20) = FISH_XC_SYM(8:10,8:10)
FISH_BIG_XC(1:7,18:20) = FISH_XC_SYM(1:7,8:10)
FISH_BIG_XC(18:20,1:7) = FISH_XC_SYM(8:10,1:7)

% Final summation
FISH_SYM = FISH_BIG_GCsp + FISH_BIG_XC

I have still terms non-nul in the FISH_SYM Symbolic matrix like

sp_29_31 + xc_19_21, sp_30_31 + xc_20_21, sp_31_31 + xc_21_21

Do you understand my issue ? I would like instead terms like this :

xc_19_21, xc_20_21, xc_21_21

since

sp_29_31, sp_30_31, sp_31_31

are null.

The trick would allow to assign zeros values when I fill FISH_BIG_GCsp and FISH_BIG_XC , but I don't know how to combine the lines

FISH_SYM = zeros(31,31,'sym');
FISH_BIG_GCsp = zeros(31,31,'sym');
FISH_BIG_XC = zeros(31,31,'sym');

FISH_SYM = sym('xc_', [31,31], 'positive');
FISH_BIG_GCsp = sym('sp_', [31,31], 'positive');
FISH_BIG_XC = sym('xc_', [31,31], 'positive');

Any help is welcome ! Best regards

[petit]

error of beginner :

problem solved by simply FISH_BIG_Gcsp and FISH_BIG_XC to zeros "symbolic" arrays and after fill them with subarrays FISH_GCsp_SYM and FISH_XC_SYM