Timestamp on X axis from datetime

Hello, I have made a plot already which looks like that:

X axis is a time of observation. It is a vector of [0, 5, 10, 15 ...]. I would like to use a timestemps as a X axis ticks. I have a variable ts, which is the timestamp of each sample. How should I change my X axis description using a plot browser to timestams. Format of my timestamps is 'dd.MM.yyyy HH:mm:ss'

Answer 1

[Jorik]

Hi Maksym, if you convert your x vector to a datetime, you can simply plot the datetime vector against your values for the 3 lineplots and already get meaningful labels for the timestamps.

Example:

x = today + (0.5:0.01:0.6);
x_datetime = datetime(x, 'ConvertFrom', 'datenum');
plot(x_datetime, rand(size(x)))

As you can see, I start with simple datenum doubles, convert it to datetimes and if you zoom into the plot or use a different time-scale, the x-labels are automatically changed to show meaningful values and details.

If you need the specific format you mentioned, you can specify it with a line like this:

xtickformat('dd.MM.yyyy HH:mm:ss')

All of this is possible since R2016b or do you need to use an older version of MATLAB?

[Walter Roberson]

If YourTimestamps is a cell array of character vectors in 'dd.MM.yyyy HH:mm:ss' format, then you would probably want something like

x_datetime = datetime(YourTimestamps, 'InputFormat', 'dd.MM.yyyy HH:mm:ss');

[Maksym Zawrotny]

Thank you, Jorik!

It's just the thing I needed.

[Laukik Avinash Kharche]

Hello,

I have a question regarding the answer you gave. I use it for a quite similar purpose as the questioner here. But when I use your code for getting x_datetime, The date I see there is 31-Dec--0001. I wonder how I could put the correct date there ? I have the Time stamp in decimals(only for time and not the date) and they get converted to DD-MMM--YYYY hh:mm:ss after using the date time function.

Thank you,

Laukik.

[Jorik]

You either need to choose a date (I would only do this is you knew which day the data is referring to) or use a different datatype. You could e.g. use duration instead of datetime to leverage the smart label capabilities without having actual dates.

E.g. if you want to plot a sine for t = 0-60 seconds duration:

t = 0:0.1:60;       % seconds
f = 0.05;           % freq
v = sin(2*pi*f*t);  % calculate the sin(2πft)
t_d = duration(seconds(t));
plot(t_d, v)        % plot t as duration against v