Plot over time milliseconds

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Eduardo Santos
Eduardo Santos on 11 Oct 2019
Commented: Jon on 11 Oct 2019
I'm trying to plot a number over time. The idea is to show on X-axis the date with milliseconds format.
The code below is not working properly, could some one help me?
figure(1)
while(1)
timestr = datetime(clock,'InputFormat','yyyy-MM-dd HH:mm:ss.S', 'Format', 'yyyy-MM-dd HH:mm:ss.SSS');
plot(timestr, rand(1));
pause(0.01)
end

Accepted Answer

Jon
Jon on 11 Oct 2019
Edited: Jon on 11 Oct 2019
I'm not quite clear on what you are trying to accomplish but it looks like some how you want to see the plot continue to evolve as time goes along.
You could modify your code as follows and see the points continuously updated, the key is to use the hold on command:
% assign number of iterations
numIter = 1000;
% open new figure
figure
hold on % so figure isn't cleared with each plot command
% initialize previous values for connecting the dots
tOld = datetime('now');
yOld = rand(1);
% enter plotting loop
for k = 1:numIter
t= datetime('now');
y = rand(1);
% plot data up to the current iteration
plot([tOld,t], [yOld,y],'-bo');
xtickformat('yyyy-MM-dd HH:mm:ss.SSS')
tOld = t;
yOld = y;
pause(0.01)
end
hold off
Note, I made the code loop for a fixed number of iterations rather than have to ctrl-c to end the infinite while loop that you had.
Also a few other cleanup items, the clock command returns a six element date vector. If you call datetime(clock) it must first convert the clock value to a datetime. Instead just use datetime('now'). There is no need for formatting the value returned by calling datetime('now'), that is handled by the xtickformat
In the above code I connected the data points with lines. If you don't need the dots connected by lines then you don't need to save the previous values, you can just plot t and y with a symbol
  4 Comments
Eduardo Santos
Eduardo Santos on 11 Oct 2019
Wow.
Thanks again. That was exactly I was looking for!
Jon
Jon on 11 Oct 2019
Excellent! Glad that is working for you.

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