For loop preallocation warning?

Hello all,

Even the code works properly, I get a warning flag that advice me to preallocate all of the variables that I am accumulating during the execution of the code, do you know how to deal with this issue?, in order to debug and make faster the execution of the code.

Thanks in advance!.

%To simulate the 12 months at one click
current_path = pwd;
tic
load DATA_HILL.mat
PV_MAX_=[];
DEV_PV_=[];
SOC_=[];
month_=[];
PV_irr_=[];
Dev_2_=[];
z=zeros(12,6);

for month_number=1:12
    
    sim('HILL_V2.slx')
    disp(month_number);
    
    bdclose('HILL_V2.slx');
    
    %%%%%%
    %%%%Data upload
    load Power_PV.mat
    load SOC.mat
    load month
    load Irr
    %%%Results format
    format Eng
    %%%%Variables analysed in this study case
    PV_MAX=max(Power_PV);
    %
    DEV_PV= (PV_MAX/189000)*100;
    %
    SOC= min(SOC);
    m=mean(month);
    PV_irr=max(Irr)*189;
    Dev_2=(1-(PV_MAX/PV_irr))*100;
    
    % % % % All of the accumulated variables in the for loop
    PV_MAX_=[PV_MAX; PV_MAX_];
    DEV_PV_=[DEV_PV; DEV_PV_];
    SOC_=[SOC; SOC_];
    month_=[m; month_];
    PV_irr_=[PV_irr; PV_irr_];
    Dev_2_=[Dev_2; Dev_2_];
    
    cd(current_path);
end

A=flip([month_ SOC_ PV_MAX_ DEV_PV_ PV_irr_ Dev_2_].*z);

%%%%To creat a table in order to represent the results of the simulation
% RowName={'Month', 'SOC_min(%)', 'PV_MAX (kW)', 'DEV_PV (%)', 'PV_irr (kW)', 'Dev_2 (%)'};
LastName=flip({'Jan';'Feb';'Mar';'Apr';'May';'Jun';'Jul';'Aug';'Sep';'Oct';'Nov';'Dec'});

T=table(month_, SOC_, PV_MAX_, DEV_PV_, PV_irr_, Dev_2_,...
     'RowName', LastName);
disp(T)
toc

[Steven Lord]

In the interest of improving the documentation, was there any part of the documentation page "Preallocating Arrays" linked at the end of the first paragraph in the "Suggested Action" section of the Code Analyzer message that was unclear or that you expected to contain more information?

[Tony Castillo]

In and overall view it results some confusing to me, maybe because I implemented and the warning is still on.

Answer 1

[Ameer Hamza]

Here is a general way.

If you use the following codes, you will get a warnings

x = []
for i = 1:10
    x(i) = sin(i); % sin(i) used as example
end
% or
x = []
for i = 1:10
    x = [x sin(i)]
end

You can solve the warning by pre-allocating and use indexing to assign elements

x = zeros(1, 10)
for i = 1:10
    x(i) = sin(i); % sin(i) used as example
end

For your code, following will work

%To simulate the 12 months at one click
current_path = pwd;
tic
load DATA_HILL.mat
PV_MAX_=zeros(12,1);
DEV_PV_=zeros(12,1);
SOC_=zeros(12,1);
month_=zeros(12,1);
PV_irr_=zeros(12,1);
Dev_2_=zeros(12,1);
z=zeros(12,6);

for month_number=1:12
    
    sim('HILL_V2.slx')
    disp(month_number);
    
    bdclose('HILL_V2.slx');
    
    %%%%%%
    %%%%Data upload
    load Power_PV.mat
    load SOC.mat
    load month
    load Irr
    %%%Results format
    format Eng
    %%%%Variables analysed in this study case
    PV_MAX=max(Power_PV);
    %
    DEV_PV= (PV_MAX/189000)*100;
    %
    SOC= min(SOC);
    m=mean(month);
    PV_irr=max(Irr)*189;
    Dev_2=(1-(PV_MAX/PV_irr))*100;
    
    % % % % All of the accumulated variables in the for loop
    PV_MAX_(i)=PV_MAX
    DEV_PV_(i)=DEV_PV;
    SOC_(i)=SOC;
    month_(i)=m;
    PV_irr_(i)=PV_irr;
    Dev_2_(i)=Dev_2;
    
    cd(current_path);
end

A=flip([month_ SOC_ PV_MAX_ DEV_PV_ PV_irr_ Dev_2_].*z);

%%%%To creat a table in order to represent the results of the simulation
% RowName={'Month', 'SOC_min(%)', 'PV_MAX (kW)', 'DEV_PV (%)', 'PV_irr (kW)', 'Dev_2 (%)'};
LastName=flip({'Jan';'Feb';'Mar';'Apr';'May';'Jun';'Jul';'Aug';'Sep';'Oct';'Nov';'Dec'});

T=table(month_, SOC_, PV_MAX_, DEV_PV_, PV_irr_, Dev_2_,...
     'RowName', LastName);
disp(T)
toc

[Tony Castillo]

Dear Hamza,

Following your guidelines, I got these two problems:

1-Error using table (line 326)

Array indices must be positive integers or logical values.

Error in Untitled (line 39)

PV_MAX_(i)=PV_MAX;

and

2-The warning messages are still on.

Are we missing anything?

[Ameer Hamza]

Sorry! I made the mistake when typing these lines of code

PV_MAX_(month_number)=PV_MAX
DEV_PV_(month_number)=DEV_PV;
SOC_(month_number)=SOC;
month_(month_number)=m;
PV_irr_(month_number)=PV_irr;
Dev_2_(month_number)=Dev_2;

This should remove both errors and warnings.

[Tony Castillo]

Thank you for your help.

[Ameer Hamza]

I am glad to be of help!