How to add a datetime array to addpoints for an animated line plot?

Hi,

Let's say I have a datetime & temperature arrays as following:

Xdata Ydata

'05:00:00.048' 41

'05:00:00.052' 42

'05:00:00.056' 40.5

'05:00:00.060' 43

'05:00:00.064' 44

'05:00:00.068' 45

'05:00:00.072' 45.5

'05:00:00.076' 46

'05:00:00.080' 47

'05:00:00.084' 47.5

'05:00:00.088' 48

I would like to plot an animation line using addpoints. "addpoints" needs Xdata to be a double but I need to plot it as a datetime object.

Help me understand if there's another way around this.

Thanks,

Sun

Answer 1

[Walter Roberson]

Unfortunately, animatedLine only permits double()

https://www.mathworks.com/help/matlab/ref/animatedline.html#d117e28260

There are some obscure circumstances in plotting under which datetime objects will automatically be converted to doubles, but this is not one of those circumstances. :(

[Eric Prandovsky]

Previous examples show converting to serial date number using datenum

datenum(datetime)

ans = 7.3893e+05

But the datenum documentation says it's no longer recommended, any idea what the new suggested method is?

[Noah Prisament]

The "animatedline" now supports "datetime" values natively, so this is the new suggested method. This will also show the proper ruler on each axis. See my answer below for example syntax.

Answer 2

[Ajay Kumar]

Try this:

Convert the datetime values to numbers using datenum.

Fetch these datenum values as x parameter to addpoints.

While plotting convert these datenum values to datetime again using datetime and 'ConvertFrom'.

I hope it works.

[Sun]

Kumar,

Thanks for the response. addpoints itself plots the data. I am not able to do addpoints first and then convert the data for sake of a plot.

This is what I used:

h = animatedline('Marker','o');
addpoints(h,Xdata,Ydata);

This is the error: Error using matlab.graphics.animation.AnimatedLine/addpoints Invalid type for argument X. Type should be double.

I can try

Xdata_num = datenum(Xdata);
addpoints(h,Xdata_num,Ydata);

But plotting Xdata_num doesn't help as data constitutes to date which is the same for all time points.

Answer 3

[Noah Prisament]

The "animatedline" now supports all numeric datatypes as well as datetimes and durations for all axes as of R2023a!

In order to plot your data on an "animatedline" you can now utilize the following example:

h = animatedline(NaT, NaN);
addpoints(h, Xdata, Ydata);

or to initialize the "animatedline" with data:

h = animatedline(Xdata, Ydata);

[unknown]

How to use animatedline to draw figure with datetime in app designer UiAxes ?

An occurs error when use addpoints .

app.aline=animatedline(app.UIAxes,app.data.time,app.data.(app.figname));          
addpoints(app.aline,datetime(app.data.time(end),'Format','yyyy-MM-dd HH:mm:ss'),app.data.(app.figname)(end))

Matlab version is R2024b

[Noah Prisament]

Hi, what is the error that you are experiencing, can you send the full error text in a reply?

A potential issue is if your current axes already has non-datetime data on the x-axis. A given axes can only have either numeric or non-numeric data on either axis.