MATLAB: Fast subsetting or indexing of data

MATLABwithtol

I am working with large datasets which I am subsetting into various categories and saving as smaller files. What I am doing right now is working but it is quite time consuming and error prone, as it involved a lot of copy and paste.
For example, I have many files I have split into those with boats and those without boats. I then split those into season. Would there be a faster way to do this where I apply the same command to prescribed set of variables?
%% Comparisons... Season using water temp
boatsAbsent_t=boatsAbsent.Var1; %time variables
[BA_spring, BA_summer, BA_autumn, BA_winter]=indexSeasons(boatsAbsent_t); %index times into seasons
boatsPresent_t=boatsPresent.Var1;       
[BP_spring, BP_summer, BP_autumn, BP_winter]=indexSeasons(boatsPresent_t);
       
%Subset PSD outputs and write to file
S=withtol(BA_spring,seconds(1));
BA_spring=boatsAbsent(S,:);
writetable(timetable2table(BA_spring),...
    fullfile(folder,strcat(site,'_PSD_boatsAbsent_Spring.csv')));
S=withtol(BA_summer,seconds(1));
BA_summer=boatsAbsent(S,:);
writetable(timetable2table(BA_summer),...
    fullfile(folder,strcat(site,'_PSD_boatsAbsent_Summer.csv')));
S=withtol(BA_autumn,seconds(1));
BA_autumn=boatsAbsent(S,:);
writetable(timetable2table(BA_autumn),...
    fullfile(folder,strcat(site,'_PSD_boatsAbsent_Autumn.csv')));
S=withtol(BA_winter,seconds(1));
BA_winter=boatsAbsent(S,:);
writetable(timetable2table(BA_winter),...
    fullfile(folder,strcat(site,'_PSD_boatsAbsent_Winter.csv')));
     
S=withtol(BP_spring,seconds(1));
writetable(timetable2table(BP_spring),...
    fullfile(folder,strcat(site,'_PSD_boatsPresent_Spring.csv')));
S=withtol(BP_summer,seconds(1));
writetable(timetable2table(BP_summer),...
    fullfile(folder,strcat(site,'_PSD_boatsPresent_Summer.csv')));
S=withtol(BP_autumn,seconds(1));
writetable(timetable2table(BP_autumn),...
    fullfile(folder,strcat(site,'_PSD_boatsPresent_Autumn.csv')));
S=withtol(BP_winter,seconds(1));
writetable(timetable2table(BP_winter),...
    fullfile(folder,strcat(site,'_PSD_boatsPresent_Winter.csv')));

Best Answer

Whenever you find yourself copy-pasting code in Matlab, you should consider an array.
seasons={'Spring','Summer','Autumn','Winter'};
boatsPresent_t=boatsPresent.Var1; %time variables

boatsAbsent_t=boatsAbsent.Var1; %time variables
BP=cell(1,4);BA=cell(1,4);
[BP{:}]=indexSeasons(boatsPresent_t); %index times into seasons

[BA{:}]=indexSeasons(boatsAbsent_t); %index times into seasons
for n=1:numel(seasons)
    S=withtol(BP{n},seconds(1));
    BP_part=boatsPresent(S,:);
    writetable(timetable2table(BP_part),...
        fullfile(folder,strcat(site,'_PSD_boatsPresent_',seasons{n},'.csv')));
    
    S=withtol(BA{n},seconds(1));
    BA_part=boatsAbsent(S,:);
    writetable(timetable2table(BA_part),...
        fullfile(folder,strcat(site,'_PSD_boatsAbsent_',seasons{n},'.csv')));
end
If you have more states than just present and absent you should consider putting those states in an array so you can use it to generate logical indices.
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