Setting time on X-axis for over 24 hours

I have to plot time on X-axis with the time close to 10^6 secs. how can I show them in hours? I tried datetick('x','HH:MM') But it sets the time to 00:00

What i would like to see is something like this 'HHH:MM'

Thanks in advance

Answer 1

[dpb]

Time axes in Matlab are in either (traditional) datenum to use datetick or the newer time class (R2014?, maybe?). But, neither knows how to handle hours other than traditional 24-hr/day so that doesn't help...

Put the following into a helper function so you can just call it with the time vector but given an array of times in seconds, t, the following should do what you're looking for--

r=t/3600;   % time in hours and fractions to save multiple divides
hr=fix(r);  % the whole hour portion for each
mn=round((r-hr)*60);  % and the minute in integer

Example use --

>> t   % similar to your start for short example
t =
   2974800     2974860     2974920     2974980     2975040     2975100
>>  plot(r,randn(size(r)))  % a typical plot
>> xlim([r(1) r(end)])      % range the axes over same values
>> set(gca,'xtick',r)       % and set tick marks to match
>> set(gca,'xticklabel', ...
       cellstr(arrayfun(@(h,m) sprintf('%03d:%02d',h, m),hr,mn,'uni',0)))

The last is the "trick" to format the hr:min for labeling axis tick per desire of HHH:MM

You'll need to select the tick marks at some interval much larger than 1 as illustrated here to not have too many; whatever is differential between N minutes would be the logical way to do this.

Sorry I didn't catch on to the real problem first pass...

[rubina mahtab]

lets say if I am taking the time on 3rd feb 2016 10:20, which sums upto 2974800 seconds. i want the display to show 826:20. the datetick that you have mentioned will convert the display again to HH:MM

[dpb]

Oh, old eyes missed the third 'H' on the initial posting, sorry. I don't know if the new '%D' format string will convert to number of hours cumulative or not; the traditional datestr (and hence datetick) cannot as I now presume you'd already discovered.

Best I can think of is to use the internal datenum logic to convert with rollover to generate the actual date components and then build the actual time as wanted...

Sample starting with your starting time and adding some to it; you'd use your actual seconds vector of course...

[y,m,d,h,mn,s]=datevec(datenum(2016,0,0,0,0,2974800);

Then build the hourly fractional number from these--

>> (sum(eomday(y,1:m-1))+d)*24+h+mn/60
ans =
826.3333
>>

Alternatively, just begin w/ your seconds values and divide and remainder and repeat for the smaller time periods.