Plotting data against time

Edit: I've added the .mat file and a code which shows what i'm trying to do.

% timex=datetime(time_orginal,'Format','dd/MM/yy HH:mm:ss:SSS') does not
% work and results in a error. Hence the loop.
for i=1:length(time_orginal)
timex(i)=datetime(time_orginal(i),'Format','dd/MM/yy HH:mm:ss:SSS')
end

plot(timex,datax)

Using the .mat file provided and this code results in the following plot:

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Hi all. I have two arrays that i'm trying to plot together. Timex is a 10x1 datetime and datax is 10x1 double.

when I do

 plot(timex,datax) 

I dont get what i'm after, which is date and time on x axis and data on y axis.

I dont understand why the datetime is not showing up on the x-axis. Any help is much appreciated.

the data:

timex = 
   18/09/21 04:32:02:000
   18/09/21 04:32:02:200
   18/09/21 04:32:02:400
   18/09/21 04:32:02:600
   18/09/21 04:32:02:800
   18/09/21 04:32:03:000
   18/09/21 04:32:03:200
   18/09/21 04:32:03:400
   18/09/21 04:32:03:600
   18/09/21 04:32:03:800

and

datax =
   -0.0200
   -0.0200
   -0.0300
   -0.0200
   -0.0200
   -0.0200
   -0.0200
   -0.0300
   -0.0300
   -0.0300

[Walter Roberson]

 plot(t,x)

That involves two variables that we do not know anything about. You have told us about timex and datax but not about t and x

[Andy Thor]

whoops. That was supposed to be plot(timex,datax) . Edited.

Answer 1

[the cyclist]

New answer based on your update.

The problem is that your original time series is in two different formats -- not including the milliseconds when the time is exact to the second.

I'm frankly not certain how datetime() handled the conversion in this case, but if you compare your version of timex and mine, you'll see the difference.

There may be a more elegant way to handle that, but this works in a kludgy way:

load noGoodPlot.mat

timex          = datetime(time_orginal,         'InputFormat',"dd/MM/yy HH:mm:ss:SSS");
timex(1:5:end) = datetime(time_orginal(1:5:end),'InputFormat',"dd/MM/yy HH:mm:ss");

figure
plot(timex,datax);

Ideally, the solution to this would resolve the data format issue upstream, in time_orginal.

[Andy Thor]

Thank you for your help in this matter.

Answer 2

[the cyclist]

Works for me, when I correctly specify valid dates using the input format.

I'm guessing that your datetime is somehow messed up. It would be helpful if you uploaded your variables in a MAT file (using the paperclip icon), so we can see what you are actually working with.

timex = datetime( ...
   {'18/09/21 04:32:02:000'; ...
   '18/09/21 04:32:02:200'; ...
   '18/09/21 04:32:02:400'; ...
   '18/09/21 04:32:02:600'; ...
   '18/09/21 04:32:02:800'; ...
   '18/09/21 04:32:03:000'; ...
   '18/09/21 04:32:03:200'; ...
   '18/09/21 04:32:03:400'; ...
   '18/09/21 04:32:03:600'; ...
   '18/09/21 04:32:03:800'},'InputFormat','dd/MM/yy HH:mm:ss:SSS');

datax = [ ...
   -0.0200;
   -0.0200;
   -0.0300;
   -0.0200;
   -0.0200;
   -0.0200;
   -0.0200;
   -0.0300;
   -0.0300;
   -0.0300];

figure
plot(timex,datax)

[Andy Thor]

Thanks for the reply. I´ve added some more information and the .mat file.