retrieving solar irradiance data through webread function

how can i retrieve solar irradiance data of 24 hours from https://www.newquayweather.com/pwsWD/index.php in MATLAB through webread function?

Answer 1

[Cameron]

This is a way to get it instantaneously.

url = 'https://www.newquayweather.com/pwsWD/index.php';
w = webread(url);
loc1 = strfind(w,'W/m²');
B = str2num(string(regexp(w(loc1-10:loc1),'\d*','Match')));
fprintf('Solar irradiance at %s is %d W/m²',datetime('now'),B)

Solar irradiance at 09-Mar-2023 15:18:03 is 174 W/m²

[Cameron]

Here's a way to run it over an entire 24 hours.

clear
url = 'https://www.newquayweather.com/pwsWD/index.php';
SecBetweenReading = 10; %seconds between each reading
for x = 1:3600*24/SecBetweenReading %3600 seconds in an hour, 24 hours
    w = webread(url); %read the web page
    loc1 = strfind(w,'W/m²'); %find where W/m2 is
    B = str2num(string(regexp(w(loc1-10:loc1),'\d*','Match'))); %get only the number
    dt(x,1) = datetime('now'); %save datetime
    tsi(x,1) = B; %save your solar irradiance
    disp(dt(end,1)) %display the most recent time the data was read
    pause(SecBetweenReading) %pause for a given amount of time
end
plot(dt,tsi,'-o') %plot at the end

[Muhammad]

thanks cameron for the guidance, is there any other way to visualize solar irradiance data for 24 hours. i run the above code and it gives me 10-Mar-2023 18:08:25

10-Mar-2023 18:08:37

10-Mar-2023 18:08:48

10-Mar-2023 18:09:00

10-Mar-2023 18:09:12

10-Mar-2023 18:09:23

10-Mar-2023 18:09:35

10-Mar-2023 18:09:47

in command window. i want to visualize it also.

[Cameron]

There are a couple of things you can do. The reason I didn't plot the tsi vs date is because if you were to close the graph, the program would stop. You can either run the script until 1 whole day has passed or you can hit Control+C to manually stop the program. The variables for dt and tsi should be in your workspace up until you stopped the program. The code I will paste below will save your data to a .txt file you specify prior to reading data from the website. So you can open this file to see all the data that's been collected over a period of time. I did notice while I was running this script that sometimes the url said the solar irradiance was 0 W/m2 which wasn't true, but that's what was on the url so that's what was read by the program.

clear
url = 'https://www.newquayweather.com/pwsWD/index.php'; %your url
[file,path,indx] = uiputfile('.txt'); %save a file as a .txt. you can change this to your preferred extension
if indx == 0; msg = 'No path selected.'; error(msg); end %user hits Cancel or closes uiputfile prompt
cd(path) %change path to the one designated in uiputfile
fileID = fopen(file,'a'); %open file and append any data
SecBetweenReading = 10; %seconds between each reading
opt = weboptions('Timeout',60); %set the web timeout to 60 seconds
fig = figure; %create figure
ax = uiaxes(fig); %create axes
for x = 1:3600*24/SecBetweenReading %3600 seconds in an hour, 24 hours divided by seconds between reading
    w = webread(url,opt); %read the web page
    loc1 = strfind(w,'W/m²'); %find where W/m2 is
    B = str2num(string(regexp(w(loc1-10:loc1),'\d*','Match'))); %get only the number
    dt(x,1) = datetime('now'); %save datetime
    tsi(x,1) = B; %save your solar irradiance
    fprintf(fileID,'%s,%d\n',dt(x,1),tsi(x,1));
    disp(dt(end,1)) %display the most recent time the data was read
    disp(tsi(end,1)) %display the most recent tsi the data was read
    if isgraphics(ax) %if you have not closed the plot 
        plot(ax,dt,tsi,'-o') %plot all data
    end
    pause(SecBetweenReading) %pause for a given amount of time
end
fclose(fileID);

If you're having difficulties deleting files, you may have not used the fclose() function on one of your .txt files. I would use

fclose('all')

if you're getting an error from your computer saying MATLAB has a certain file open.

[Muhammad]

Thanks alot Cameron for the guidance.