converting seconds to date in a plot

Hello. Im trying to plot a 'Huge' variable which will contains more than 1,000,000 rows. Initially, X axis is formatted as seconds. I would like to set(define) a start date/time/seconds, like 8/14/2017 10:03:44.22334 and plot it on the graph as the time-date-hours-mins-seconds format. I took a look at related functions but I could not really get it. Can anyone help with it? Thank you!

Answer 1

[mizuki]

If you write a question with your sample code, it is easy for us to find out your problem as well as you would get more suitable answers.

DATETICK allows you to change the ticklabel of the figure with datetime format.

timestr = datetime('08/14/2017 10:03:44.22334', 'InputFormat', 'MM/dd/yyyy HH:mm:ss.SSSSS')+ seconds(0:1:10)
h = plot(timestr, rand(1,11), 'o');
datetick('x', 'DD-HH-mm-ss')

Answer 2

[Peter Perkins]

The answer depends on what version of MATLAB you are using. Using datetick with a plot of datetimes probably works prior to R2016b, but going forward it's not what you'd want to do. In R2016b or later, do this:

>> t = seconds(1000*sort(rand(100,1)));
>> x = 1:100;
>> plot(t,x) % plot data vs. time in seconds
>> d = datetime(2017,8,14,10,3,44,223.34,'Format','MM/dd/yyyy HH:mm:ss.SSSSSS') + t;
>> plot(d,x) % plot data vs. absolute time

If you don't like the date/time format that plot chooses automatically, you can set it explicitly:

>> ax = gca; ax.XAxis.TickLabelFormat = 'dd-HH-mm-ss'