Continuous plotting with nested for loops

clc
DOY = 1;
Lref = 0;
L = 4.23;
phi = 55.86;
gamma = 0; %0 is facing South
beta = 26; %26 degree tilt of front window 
Area = 1.206; %not accurate
DirectNormalData = WeatherData(:,3,:);
DiffuseHorizontalData = WeatherData(:,1,:);
Q = 0;
DOY = 1;
DOYstart = 1;
if DOYstart == 1
    DOYinitial = 1;
else 
    DOYinitial = 73*DOYstart;
end
for j = DOYinitial:DOY %20 minute iterations for one day
    for i=1:72
        
        tref = i/(3*DOY);
        %Declination angle
        dec = 23.5*sin((360*(284+DOY))/365);
        %Hour angle
        B = 360*(DOY-81)/364;
        E = 9.87*sin(2*B)-7.35*cos(B)-1.5*sin(B);
        tsol = tref + (4*(Lref-L)+E)/60;
        h = 15*(tsol-12);
        %Solar altitude 
        as = asin(cos(phi)*cos(h)*cos(dec)+sin(phi)+sin(dec));
        %Surface Solar azimuth
        gammaS = acos((sin(phi)*cos(h)*cos(dec)-cos(phi)*sin(dec))/cos(as));
        w = gammaS-gamma;
        %Direct Beam
        IB = DirectNormalData(i);
        %Direct Beam intensity in vertical direction
        IBx = IB*(cos(as)+sin(beta)*cos(w)+sin(as)*cos(beta));
        %diffuse horizontal component
        IDh = DiffuseHorizontalData(i);
        %using the isentropic sky model
        IDbeta = IDh*(1+cos(beta))/2;
        %Total radiation falling on the surface is
        Itot = IBx + IDbeta;
        Q = Itot*Area;
        hold on
        plot(i,Q, "-r.", 'MarkerSize',7)
        title('Solar Radiation Heat Transfer against Time', 'Fontsize',16)
        xlabel('Time (20 minute iterations)', 'fontsize', 14)
        ylabel('Heat transfer into cabin (W)', 'fontsize', 14)
    end 
    hold on 
end

WeatherData is a 3D array with weather data for each day stored as 2D arrays with the 3rd dimension being the days in a year

I want to be able to plot Q against time

i is indicating 20 minute step sizes, hence i=1:72 is a days worth of calculations

I know plotting I against Q won't work seeing as the range of i keeps repeating for iterations of j

I initially only had one for loop indicated as:

for i = DOYinitial:72*DOY

This caused errors for tref because tref is the reference time in 24 hour time. For each new day I need tref to start at tref=1/3 and continue in increments of 1/3.

The following script is used to convert the data file into a 3D array

    close all
    clear
    clc
    %% Load Data
    hours = 24;
    days = 365;
    content = strsplit(fileread("GBR_SCT_Glasgow.AP.031400_TMYx.2007-2021.clm"));
    for i = 1:days
        climateDataString(:,:,i) = content(1,89+((i-1)*29):89+((i-1)*29)+23);
    end
    climateDataString = permute(climateDataString, [2 1 3]);
    for i = 1:days
        for ii = 1:hours
            climateData(ii,:,i) = str2double(strsplit(cell2mat(climateDataString(ii,1,i)), ','));
        end
    end
    S=size(climateData);
    WeatherData = interp1(climateData,linspace(1,S(1),3*S(1)));

any help is greatly appreciated. Thank you

[Torsten]

I think without the possibility to test the code with access to the matrix "WeatherData", nobody will try to answer your question.

[Daniel Lynch]

@Torsten Thank you for the advise. I have edited the post to include the file and the script I used to read the data.

Answer 1

[SANKALP DEV]

Hey Daniel,

I understand you are trying to calculate the heat transfer into a cabin due to solar radiation, using Weather Data and want to plot heat transfer (Q) against time.

Please consider following steps to plot they heat transfer (‘Q’) against time:

• Initialize arrays Q and time to store calculated values: Create empty arrays to hold the heat transfer values (Q) and the corresponding time intervals (time).
• Adjust the loop structure to iterate through the desired range of days (DOYinitial:DOY) and within each day, iterate through the 20-minute intervals (i = 1:72). 
• Calculate ‘tref’ by dividing i by 3 to represent 20-minute intervals: Compute the time reference (‘tref’) by dividing the interval index (‘i’) by 3, assuming each increment of 1/3 represents 20 minutes.
• Store calculated Q values and corresponding time intervals in Q and time arrays: Append the calculated heat transfer values (Q) to the Q array and the corresponding time intervals (tref) to the time array.
• Plot Q against time.

After examining your code, I have implemented the following modifications:

1. Adjusted the calculation of ‘tref’ to assume that 1/3 represents 20 minutes. This adjustment ensures that the time intervals align correctly with the data.
2. Modified the indexing of ‘DirectNormalData’ and ‘DiffuseHorizontalData’ to access the data for the current day (‘j’ index added). This ensures that the correct weather data is used for each iteration.
3. Replaced the inner loop's plotting code with the code to store ‘Q’ and time values at each iteration. This allows us to collect the calculated values for later plotting.

Please refer to the following code:

% Initialize arrays to store the heat transfer values (Q) and corresponding time values 
Q = []; 
time = []; 
% Iterate through the desired range of days 
for j = DOYinitial:DOY 
    % Determine the number of intervals for the current day 
    intervals = 72; 
    % Iterate through the 20-minute intervals 
    for i = 1:intervals 
        % Calculate the time reference (tref) to represent 20-minute intervals 
        tref = i / 3; 
        % Calculate the heat transfer (Q) based on the given equations and weather data 
        Q_value = (DirectNormalData(j, i) + DiffuseHorizontalData(j, i)) * Area * (sind(theta) + sind(phi)) * (cosd(theta) + cosd(phi)) / 2; 
        % Store the calculated Q value and its corresponding time 
        Q = [Q, Q_value]; 
        time = [time, tref]; 
     end 
end 

% Plot the heat transfer (Q) against time 
plot(time, Q); 
xlabel('Time (20-minute intervals)'); 
ylabel('Heat Transfer (Q)'); 
title('Heat Transfer into the Cabin over Time'); 

Hope this helps.