Datetick does not set x-ticks accurately

Hello Community, I got a problem using datetick in my figure. Here is what I want:

-time printed on my x-axis as "lap time" using the format "MM:SS" with speed on y-axis

Here is my code so far:

tsec=time_s(1:5266,1);
v_soll=v_target_kmph(1:5266,1);

axes1 = axes;
hold(axes1,'on');

plot(tsec,v_soll,'DisplayName','Speed','LineWidth',2);

xlabel('Time [mm:ss]','FontSize',14,'Interpreter','latex');
dateFormat = 15; % or dateFormat = 'MM:SS';
datetick('x',dateFormat, 'keeplimits', 'keepticks')

ylabel({'Speed [kmh]'},'FontSize',14,'Interpreter','latex');

   xlim(axes1,[0 530.893315881894]);

   ylim(axes1,[0 300]);
  box(axes1,'on');

set(axes1,'FontName','SansSerif');

tsec looks like this:

0
0.100000000000000
0.200000000000000
0.300000000000000
0.400000000000000
0.500000000000000
0.600000000000000
0.700000000000000
0.800000000000000
0.900000000000000
1
1.10000000000000
1.20000000000000
1.30000000000000
1.40000000000000
1.50000000000000
1.60000000000000
1.70000000000000
1.80000000000000
1.90000000000000
2
2.10000000000000
...... (until)
526.500000000000

Using datestr(tsec/24/3600, 'MM:SS'); makes it correctly displayed as I want it but I cant use that in the plot (i.E. 08:46)

Using the Code above gives me the following result attached in file

Answer 1

[Walter Roberson]

datetick works with datenum which are defined as being in terms of full days and fractions of a day. Your times are therefore incrementing by 1/10 of a day, so 2.4 hours.

With a 526 range, the default ticks are going to be nice round integers, probably the hundreds, perhaps the 50s as well. You keepticks so MATLAB will not attempt to recompute ticks that align with nice round times. And the thing is, integer datenum always correspond to midnight, so you are always going to get 00:00

Divide your seconds by the number of seconds per day, and do not keepticks

Or if you have a release since R2014b then switch to duration() objects by plotting seconds(tsec) on the x axis and do not use datetick

[Phil_Schu]

Thank you for your help. It did work with your first proposal. I couldn't make duration() work in the first attempt. (Matlab 2017a though).

So I changed my input time to

tsec=time_s(1:5260,1)/86400;

and used tsec then to plot against the Speed-Input. Deleted the keepticks and it all worked out. So thank you again!