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Rui
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Real time plot from streaming data

Asked by Rui
on 17 Sep 2013
Latest activity Commented on by Zibo Wang on 1 Jun 2017
How can I plot a graph in real time with data being streamed from yahoo.finance?
Should I use an infinite while loop or a timer? I think neither the two are the most correct solutions since one will always be constrained by their latency and one just want to update the graph whenever the variable is updated.

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4 Answers

Answer by Nathan Crosty on 17 Sep 2013

Try this code snippet I have in my inventory as an example.
t = 0 ;
x = 0 ;
startSpot = 0;
interv = 1000 ; % considering 1000 samples
step = 0.1 ; % lowering step has a number of cycles and then acquire more data
while ( t <interv )
b = sin(t)+5;
x = [ x, b ];
plot(x) ;
if ((t/step)-500 < 0)
startSpot = 0;
else
startSpot = (t/step)-500;
end
axis([ startSpot, (t/step+50), 0 , 10 ]);
grid
t = t + step;
drawnow;
pause(0.01)
end

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great! I like this, thank you so much

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Answer by Rui
on 20 Sep 2013

Thanks Nathan. But I was trying to update my plot in real time with an alternative method, other than through while loop or timer.
I have actually built the code instead with a timer and works perfectly, but I found that
"Note:   The timer object is subject to the limitations of your hardware, operating system, and software. It is not intended to be used for real-time applications.".
I was trying to figure out which could be the most correct solution to implement in real time scenarios.

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Answer by Rui
on 20 Sep 2013

Since I am using the timer to update periodically my streaming data, I note that I cannot work on Matlab while the timer is running at the same time.
Is it supposed to happen so?
It's because timer is supposed to work independently and allow one to work freely.

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Answer by Tim DeWolf on 6 Sep 2016

I'm collecting buffer/queue data from a driver in real time using a MATLAB timer in a GUI (guide) and it works. You can still use MATLAB.

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