How to group values to display in bar charts while doing data analysis

I am doing some data-analysis to see some weekly totals over time. Right now I am manually creating new tables to display everything in bar-charts, but I think that there has to be a better way. I load the data from excel, the data contains cells and doubles. The analysis I want to be doing contains only doubles. (I am using Matlab R2020b)

An example of what my data looks like:

Names = {'These';'are';'some';'random';'names';'yay'};
YearWeek = [201901;201901;201901;201902;201902;201902];
Duration = rand(6,1);
 
T = table(Names,YearWeek,Duration);

T =

  6×3 table

      Names       YearWeek     Duration
    __________    _________    ________

    {'These' }    2.019e+05    0.67874 
    {'are'   }    2.019e+05    0.75774 
    {'some'  }    2.019e+05    0.74313 
    {'random'}    2.019e+05    0.39223 
    {'names' }    2.019e+05    0.65548 
    {'yay'   }    2.019e+05    0.17119 

Now I want to make a bar chart in which I want to see the sum of the duration per YearWeek.

What I am doing right now is:

%Selecting the right data
selected_columns = [T.YearWeek,T.Duration];
 
%Sum duration per week
[year_week,~,location_year_week] = unique(selected_columns(:,1));
SumOfDurationPerWeek = zeros(height(year_week),2);
for i = 1:height(year_week)
    SumOfDurationPerWeek(i,1) = year_week(i);
    SumOfDurationPerWeek(i,2) = sum(selected_columns(location_year_week == i, 2));
end

%Plot as a bar chart
figure()
bar(SumOfDurationPerWeek(:,1),SumOfDurationPerWeek(:,2))

However I cannot believe that there is no easier way.

Shouldn't it be possible to create a bar chart immediately without summing all the values?

Answer 1

[Ameer Hamza]

See retime(): https://www.mathworks.com/help/matlab/ref/timetable.retime.html

Even using splitapply() with findgroups() will be a simpler solution.

[Tessa]

Those two are definitly better ways to prepare my data, thank you!

Does this also mean that there is no way to make a bar chart with the first table immediately?

[Ameer Hamza]

I am not aware of any such function.

[Tessa]

Okay, thanks a lot for your help!

[Ameer Hamza]

groupsummary(): https://www.mathworks.com/help/matlab/ref/double.groupsummary.html does seem to do something like this, but I haven't tried it before, so you may need to dig a bit.

[Tessa]

That might be useful as well! I'll give it a try.

Thank you!

[Peter Perkins]

If you want weekly totals, a timetable and the retime function is the most straight-forward way. But your timestamps are numeric, so you'd need to convert things like 201901 into things like datetime(2018,12,31) or datetime(2019,1,6) (depending on how you define "week of year"), so it might be easier to leave them as numeric and use groupsummary.