Trying to set Y-Axis to Minutes:Seconds for swim times. Would like to set range from 0 to 3:30 and eliminate leading zeros

%Group4_Statistics are datenums

boxplot(Group4_Statistics,'Labels',{'IM_100','Free_50', 'Breast_50','Back_50', 'Fly_50'});

title('2021 Times by Stroke', FontName = 'Arial', FontSize = 12, FontWeight = 'Bold');

ylabel('Time');

datetick('y',"MM:SS");

Answer 1

[Cris LaPierre]

Boxplot (and boxchart) do not yet support datetimes (see here), so you need to work with numeric values (like datenums), as you are doing already. ytickformat will not work. To display ylabels in "m:ss" format, you will need to manually create a string array containing your labels and manually update the ylabels.

I elected to convert your datenums to minutes, as I found it easier to work with 0-3.5 instead of 738157.0000000000 - 738157.0024305555.

I also notice these plots automatically scale the y axis, so you need to explicitly set the limits you want to have. Finally, only datetimes support a "m:ss" format, so I elected to create a vector of datetimes, set the format, and convert to string to create the ylabels.

load Swimming-Group4.mat

% convert data to times
tms = timeofday(datetime(Group4_Statistics,'ConvertFrom',"datenum"));

% plot using time converted to decimal minutes.
boxplot(minutes(tms),'Labels',{'IM_100','Free_50', 'Breast_50','Back_50', 'Fly_50'});

% set the y axis ticks and limits. Values represent time in minutes
yticks(0:0.5:3.5)
ylim([0 3.5]) % without this, the 0 and 3.5 ticks are not visible.

% create ylabels in m:ss format
yticklabels(string(datetime(2021,1,1,0,0,0,'Format',"m:ss")+minutes(0:0.5:3.5)))

I noticed you are only interested in the times. I'm curious how you collected your data to include a date as well. I suspect these times were not collected on Jan 1, 2021 at midnight. To help make the yaxis values meaningful, I stripped away the date info using the timeofday function. I suspect that my code looks more complicated because I'm also formatting the data to what I want it to be. However, if the data were just time (durations, or time measured in seconds or decimal minutes) some of this would not be necessary. For more, see the Represent Dates and Times in MATLAB page.

[Maria Baeza]

Cris,

Thank you very much for providing insight in how you arrived at your solution. It worked well and it helped me understand and learn reading your comments and text.

Originally the data came from a timekeeping system that was imported into Excel. Instead of completing the job in Excel, I am trying to use it as an opportunity to learn MatLab, so I realize it was messy..

Thank you for helping me

[Cris LaPierre]

How do you import the spreadsheet? Can you attach the original Excel file?

Answer 2

[Akira Agata]

How about the following solution?

% Sample data
t = 0.25+3*rand(100,1);

% Create boxplot
figure
boxplot(t)
d = 0:0.5:3.5;
ax = gca;
ax.YLim = [0 3.5];
ax.YTick = d;
ax.YTickLabel = compose('%d:%02d',floor(d)',mod(d*60,60)');
ylabel('Time','FontSize',12);

[Maria Baeza]

Thank you for your quick response. When I input the suggested changes (below), the Y Axis show timing information as I would like but the boxplot no longer appears? The information is type: datenum as should be in in the range of 30 seconds to 3 minutes.. which I think the label now shows but maybe that is hours?

Any suggestions would be greatly welcomed.

boxplot(Group4_Statistics,'Labels',{'IM_100','Free_50', 'Breast_50','Back_50', 'Fly_50'});
title('2021 Times by Stroke', FontName = 'Arial', FontSize = 12, FontWeight = 'Bold');
ylabel('Time');
datetick('y',"MM:SS");
d = 0:0.5:3.5;
ax = gca;
ax.YLim = [0 3.5];
ax.YTick = d;
ax.YTickLabel = compose('%d:%02d',floor(d)',mod(d*60,60)');
subtitle('Age: 11-12',FontName = 'Arial', FontSize = 10, FontWeight = 'Bold');

Answer 3

[Cris LaPierre]

Your format spec is forcing two digits for the minutes ('MM:SS'). The way to eliminate a leading zero is to only use one 'M'. However, it doesn't look like datetick supports that (see dateFormat inputs here).

The solution may be to use ytickformat instead. It supports single-digit minute formats (see here).

ytickformat('m:ss')

[Maria Baeza]

This did not work for me..

[Cris LaPierre]

Can you share your data? Save your variable Group4_Statistics to a mat file and attach it here using the paperclip icon.

[Maria Baeza]

Cris,

Attached is the Group_4_Statistics

[Cris LaPierre]

How do you load the spreadsheet into MATLAB? Can you attach the original Excel file?

[Maria Baeza]

Cris,

I had two options on the data. The first option had the data converted to seconds but then got feedback asking to show results in minutes, seconds and milliseconds. The second option came in the format we wanted to output it in but I was unable to figure out how to bring it into MatLab in that format... so I went through some gymastics converting it to datenum..

Again, any insights you could share to improve my understanding would be greatly appreciated!

[Cris LaPierre]

Since a boxplot/boxchart needs the values to be numeric, I think Example 1 is the best way to save the data. Example 2 mixes formats (some mm:ss.SS, some ss.SS) so that file would require more code.

You do not want to include 0's, so I convert them all to NaN.

In the end, the plotting code is not any simpler because I still need the data to be numeric, and since MATLAB cannot yet import a duration that does not use a colon to separate times.

% import data
ex1 = readtable("Example 1 - 2021 - Lake Olympia Swim Team - Swimmer Results.xlsx");
ex1 = standardizeMissing(ex1,0,"DataVariables",10:18);

% Create boxchart
boxchart(ex1{:,10:18})
xticklabels(ex1.Properties.VariableNames(10:18))
set(gca,'TickLabelInterpreter','none')
ylim([0 210])
yticks(0:30:210)
yticklabels(string(datetime(2021,1,1,0,0,0,'Format',"m:ss")+minutes(0:0.5:3.5)))

[Maria Baeza]

Thank you so much!!