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

Answer 1

[Infinite_king]

Hi Federico Avino,

The MATLAB Coder was unable to determine that the variable 'index_otv' would always be a scalar, leading to the error.

While analyzing the expression 'index_otv = find(index == 1)', MATLAB Coder considers the type and size of the variable 'index' but does not account for the values stored in the variable. Since 'index' can contain any values, MATLAB Coder concludes that the function call 'find(index == 1)' may return a vector.

To resolve the issue, you can first store the result in a temporary variable, 'tOTV,' and then extract the value at index 1 and store it in the variable 'OTV'.

Please find the updated code below,

function [otv1, otv2, otv3] = TCU(P_tank1, P_tank2, P_tank3, time) %#codegen
%% 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
    
    %------------------------------------------------------------------------------------%
    % Change 1 - Moved the code inside the for loop.
    % Change 2 - Values are stored in temporary variables
    % and then transferred to main variables.
    
    index_otv = find(index == 1);
    tOTV1 = Tank(index_otv, 2);
    index_otv = find(index == 2);
    tOTV2 = Tank(index_otv, 2);
    index_otv = find(index == 3);
    tOTV3 = Tank(index_otv, 2);

    OTV1 = tOTV1(1);
    OTV2 = tOTV2(1);
    OTV3 = tOTV3(1);
    
    %------------------------------------------------------------------------------------%
end




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