Dimension 1 is fixed on the left-hand side but varies on the right ([1 x 1] ~= [:? x 1]).

Good morning,

I'm writing a piece of code in a simulink block. Here the code

function [otv1, otv2, otv3] = TCU(P_tank1, P_tank2, P_tank3, time)
%% input

toll = 1; %[bar]

% coder.varsize('otv1');
% coder.varsize('otv2');
% coder.varsize('otv3');

persistent OTV1  OTV2 OTV3
if isempty(OTV1); OTV1 = 0; end
if isempty(OTV2); OTV2 = 0; end
if isempty(OTV3); OTV3 = 0; end

if time <= 0
    
    OTV1 = 0;
    OTV2 = 0;
    OTV3 = 0;
    
else
    
    Tank_unsorted =[P_tank1 OTV1
        P_tank2 OTV2
        P_tank3 OTV3];
    
    % ordine decrescente di pressione
    [Tank, index] = sortrows(Tank_unsorted, 'descend');
    
    if (Tank(1,1) - Tank(2,1)) >= toll
        
        Tank(1,2) = 1;
        Tank(2,2) = 0;
        Tank(3,2) = 0;
        
    else if (Tank(1,1) - Tank(2,1)) < toll
            Tank(1,2) = 1;
            Tank(2,2) = 1;
            Tank(3,2) = 0;
            
        else if (Tank(2,1) - Tank(3,1)) <= toll
                
                Tank(1,2) = 1;
                Tank(2,2) = 1;
                Tank(3,2) = 1;
                
            end
        end
    end
end

index_otv = find(index == 1);
OTV1 = Tank(index_otv, 2);

index_otv = find(index == 2);
OTV2 = Tank(index_otv, 2);

index_otv = find(index == 3);
OTV3 = Tank(index_otv, 2);

%% output
otv1 = OTV1;
otv2 = OTV2;
otv3 = OTV3;

I tried the logic of the code in a script, and it works: OTVn in the end contains the correct scalar. But during the execution i have the error I wrote in the title at the lines

OTV1 = Tank(index_otv, 2);

and similar. But actually OTVn contains a scalar, because it's extracted from the matrix Tank.

I have tried the solutions on the net, but none of them worked (including coder.varsize). How could i overcome the problem? Considering the goal is to generate code