Saving data from a for loop (new-ish to MATLAB!)

I have the following for loop to get barometric pressure data from the NOAA tide buoy in Bar Harbor, ME (NOAA only provides data in one month increments and I need data for three months, hence the loop)

mn_start=9; %month to start

dd_start=11; %day to start

date_BH=[];baro_BH=[];%initializing datenum and baro variables

num_mnths=3; %number of consective months to loop - note coded to just to yr=2022

for i=1:num_mnths;

begin_date=['2022' num2str(mn_start+i-1,'%02.f') num2str(dd_start)];

end_date=['2022' num2str(mn_start+i,'%02.f') num2str(dd_start-1)];

NOAAurl_Baro=['https://api.tidesandcurrents.noaa.gov/api/prod/datagetter?' ...

'begin_date=', begin_date, '&end_date=' end_date , '&station=8413320&'...

'product=air_pressure&datum=MSL&time_zone=lst_ldt&units=metric&format=csv'];

datatable=webread(NOAAurl_Baro);%getting waterlevel data from NOAA

date_BH=[date_BH table2array(datatable(:,1))'];%serial date number

baro_BH=[baro_BH table2array(datatable(:,2))'];%barometric pressure (mbars); datenum same as WL

end

When the loop closes, I only have data saved from the final iteration. How can I save data from every iteration? Thank you!

Answer 1

[Star Strider]

Save the ‘datatable’ output to a cell array —

    mn_start=9;     %month to start
    dd_start=11;    %day to start
    date_BH=[];baro_BH=[];%initializing datenum and baro variables
    num_mnths=3; %number of consective months to loop - note coded to just to yr=2022
    for i=1:num_mnths;
        begin_date=['2022' num2str(mn_start+i-1,'%02.f')  num2str(dd_start)];
        end_date=['2022' num2str(mn_start+i,'%02.f')  num2str(dd_start-1)];
        NOAAurl_Baro=['https://api.tidesandcurrents.noaa.gov/api/prod/datagetter?' ...
        'begin_date=', begin_date, '&end_date=' end_date , '&station=8413320&'...
        'product=air_pressure&datum=MSL&time_zone=lst_ldt&units=metric&format=csv'];
    datatable{i}=webread(NOAAurl_Baro);%getting waterlevel data from NOAA
%     date_BH=[date_BH table2array(datatable(:,1))'];%serial date number
%     baro_BH=[baro_BH table2array(datatable(:,2))'];%barometric pressure (mbars); datenum same as WL
    end

    datatable{1}

ans = 7200×5 table
        DateTime        Pressure    X    N    R
    ________________    ________    _    _    _

    2022-09-11 00:00     1020.3     0    0    0
    2022-09-11 00:06     1020.3     0    0    0
    2022-09-11 00:12     1020.3     0    0    0
    2022-09-11 00:18     1020.3     0    0    0
    2022-09-11 00:24     1020.3     0    0    0
    2022-09-11 00:30     1020.3     0    0    0
    2022-09-11 00:36     1020.3     0    0    0
    2022-09-11 00:42     1020.2     0    0    0
    2022-09-11 00:48     1020.2     0    0    0
    2022-09-11 00:54     1020.3     0    0    0
    2022-09-11 01:00     1020.2     0    0    0
    2022-09-11 01:06     1020.2     0    0    0
    2022-09-11 01:12     1020.3     0    0    0
    2022-09-11 01:18     1020.3     0    0    0
    2022-09-11 01:24     1020.3     0    0    0
    2022-09-11 01:30     1020.3     0    0    0

    datatable{2}

ans = 7440×5 table
        DateTime        Pressure    X    N    R
    ________________    ________    _    _    _

    2022-10-11 00:00     1023.2     0    0    0
    2022-10-11 00:06     1023.2     0    0    0
    2022-10-11 00:12     1023.2     0    0    0
    2022-10-11 00:18     1023.2     0    0    0
    2022-10-11 00:24     1023.2     0    0    0
    2022-10-11 00:30     1023.2     0    0    0
    2022-10-11 00:36     1023.3     0    0    0
    2022-10-11 00:42     1023.2     0    0    0
    2022-10-11 00:48     1023.2     0    0    0
    2022-10-11 00:54     1023.2     0    0    0
    2022-10-11 01:00     1023.1     0    0    0
    2022-10-11 01:06     1023.2     0    0    0
    2022-10-11 01:12     1023.3     0    0    0
    2022-10-11 01:18     1023.3     0    0    0
    2022-10-11 01:24     1023.3     0    0    0
    2022-10-11 01:30     1023.3     0    0    0

    datatable{3}

ans = 7200×5 table
        DateTime        Pressure    X    N    R
    ________________    ________    _    _    _

    2022-11-11 00:00       1015     0    0    0
    2022-11-11 00:06     1015.1     0    0    0
    2022-11-11 00:12     1015.2     0    0    0
    2022-11-11 00:18     1015.2     0    0    0
    2022-11-11 00:24     1015.2     0    0    0
    2022-11-11 00:30     1015.3     0    0    0
    2022-11-11 00:36     1015.4     0    0    0
    2022-11-11 00:42     1015.4     0    0    0
    2022-11-11 00:48     1015.3     0    0    0
    2022-11-11 00:54     1015.2     0    0    0
    2022-11-11 01:00     1015.3     0    0    0
    2022-11-11 01:06     1015.3     0    0    0
    2022-11-11 01:12     1015.4     0    0    0
    2022-11-11 01:18     1015.5     0    0    0
    2022-11-11 01:24     1015.7     0    0    0
    2022-11-11 01:30     1015.8     0    0    0

    
    cat_datable = cat(1, datatable{:})          % Cioncatenate All To A Single Table (Optional)

cat_datable = 21840×5 table
        DateTime        Pressure    X    N    R
    ________________    ________    _    _    _

    2022-09-11 00:00     1020.3     0    0    0
    2022-09-11 00:06     1020.3     0    0    0
    2022-09-11 00:12     1020.3     0    0    0
    2022-09-11 00:18     1020.3     0    0    0
    2022-09-11 00:24     1020.3     0    0    0
    2022-09-11 00:30     1020.3     0    0    0
    2022-09-11 00:36     1020.3     0    0    0
    2022-09-11 00:42     1020.2     0    0    0
    2022-09-11 00:48     1020.2     0    0    0
    2022-09-11 00:54     1020.3     0    0    0
    2022-09-11 01:00     1020.2     0    0    0
    2022-09-11 01:06     1020.2     0    0    0
    2022-09-11 01:12     1020.3     0    0    0
    2022-09-11 01:18     1020.3     0    0    0
    2022-09-11 01:24     1020.3     0    0    0
    2022-09-11 01:30     1020.3     0    0    0

.

[Molly Autery]

Thank you for your help! This is exactly what I was looking for.

[Star Strider]

As always, my pleasure!