How to make the live plot run in seconds?

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LuYao Guo
LuYao Guo on 2 Mar 2021
Answered: Dongyue on 21 Nov 2022
Hello,
Can somebody please help me debug this code? I'm using a EEG data where records eye blink happens every 3 seconds. And I want to plot this in real time (second). But when I use code
drawnow limitrate
The plots seems faster than I expect. I also try 'drawnow', which gives me really slow drawing.
%Plot two channels without filters
clear
clc
close all
h = figure;
%a1 = animatedline('Color',[0 .7 .7]);
axis tight
%Sampling Frequency = 250
fs = 250;
opts = detectImportOptions("blink.txt");
%opts.VariableNamesLine = 1;
C = readtable('blink.txt');
A = table2array(C(:,23));
t = (1:height(C))/fs;
%Create subplot
sph1 = subplot(2,1,1);
axis([0 10 -18000 0]);
a1 = animatedline('Color',[0 1 1]);
xlabel('time in seconds');
ylabel('uV');
title('EEG signals in channel 1');
sph2 = subplot(2,1,2);
axis([0 10 0 18000]);
a2 = animatedline('Color',[0 1 1]);
xlabel('time in seconds');
ylabel('uV');
linkaxes([sph1,sph2],'x');
for k = 1:height(C)
%Guard addpoints call with check
addpoints(a1,t(k),C.EXGChannel1(k));
hold on
addpoints(a2,t(k),C.EXGChannel6(k));
%For scrolling window
xlim([max(0,t(k)-30) max(30,t(k))]);
%ylim('auto');
%xlimit = [t(k)-30,t(k)];
%set(a1,'xlim',xlimit);
%set([a1,a2],'xlim',xlimit);
drawnow limitrate
end
I appreciate a lot for your help!
  2 Comments
Walter Roberson
Walter Roberson on 2 Mar 2021
Do not call hold on inside the loop. You are not adding any new graphics objects inside the loop.
Your animated lines are in two different subplots, but you are only adjusting the limit on one of them. You do link the 'x' properties, but you do not link the XLim properties.
LuYao Guo
LuYao Guo on 2 Mar 2021
Hi Walter, thank you for suggestions. I've edited the part based on your suggestions but the speed of plotting is not changing at all. Do you have more ideas about this? Thank you.

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Answers (1)

Dongyue
Dongyue on 21 Nov 2022
Hi LuYao, you can try to use pause(1) in your loop, which can stop the iteration for 1 second each turn. For more details, please go through the link below:

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