Plot in real time

I want to take a 2-dimensional vector and plot it, but I want to show the line being drawn as if the data is being gathered in real time. However, I'll have the data already stored in an array.

For example, if I wanted to plot y = sin(x) from x = 1 to 25, then I would use the following command:

    plot(sin(1:0.01:25));

But I want to see the curve being drawn as if it's being done in real-time. How would I do this?

Answer 1

[the cyclist]

One possible way:

x = 1:0.01:25;
y = sin(x);

n = numel(x);

figure
hold on
for i = 1:n
    plot(x(1:i),y(1:i))
    xlim([0 25])
    ylim([-1.1 1.1])
    pause(0.05)
end

[Caleb]

I had nearly this same code, but I was putting xlim and ylim outside of the loop. Thank you!

[the cyclist]

It is actually better outside the loop, as long as it is before the plotting. So, this is slightly more efficient:

x = 1:0.01:25;
y = sin(x);
n = numel(x);
figure
xlim([0 25])
ylim([-1.1 1.1])
hold on
for i = 1:n
    plot(x(1:i),y(1:i))
    pause(0.05)
end

[Alireza Madani]

Does anyone know how can we program this scenario in a way that the speed of the while/for loop is controller with the real time? For example if we want to plot y = sin(t) and t = 0 : 0.01 : 25. It actually takes 25 seconds for the MATLAB to plot this.

[Khang Nguyen]

Hi, can you graph multiple plots live at the same time?

Answer 2

[Anshul Rathore]

Don't use hold on instead use drawnow function to update your plots as it is much faster.

x = 1:0.01:25;
y = sin(x);
n = numel(x);
figure;
for i = 1:n
    plot(x(1:i),y(1:i),'-r');
    xlim([0 25]);
    ylim([-1.1 1.1]);
    drawnow;
end

[Abdoo]

could you show me, how I can plot on real time reading from usb?

[Jonathan Arias]

you have to add this line (before drawnow):

addpoints(an,x(i),y(i));

More examples: https://la.mathworks.com/help/matlab/ref/drawnow.html