plotting graph

how to plot the graph by reading the file from "name.txt" in a realtime mode with a interval of 0.004. I was able to plot the data from txt file but can't do in realtime mode... this is the code-- %from here clc %x=0:0.008:2.048 x(1)=0; fid = fopen('name.txt', 'r'); for i=1:257 d=textscan(fid,'%n',1); x=x+0.008 y(i)=x; a(i)=d{:}; end for i=1:257 pause on pause (0.004) m=y(i); n=a(i); plot (m,n) ylabel('voltage(mv)') xlabel('time(ms)') title('ECG of normal ECG') grid end fclose(fid)

%program ended any help will be greatly appreciated... thanx in advance..

Answer 1

[Avni Agrawal]

Hi @bikal shrestha,

I understand that you are trying to plot data from a text file in real-time with a specified interval in MATLAB, you can modify your code to update the plot within a loop. Here’s a streamlined version of your code that achieves this:

clc;
clear;

% Open the file
fid = fopen('name.txt', 'r');

% Initialize variables
x = 0; % Start time
dt = 0.008; % Time increment
interval = 0.004; % Real-time plotting interval
numPoints = 257; % Number of data points

% Prepare the figure
figure;
hold on;
xlabel('Time (ms)');
ylabel('Voltage (mV)');
title('ECG of Normal ECG');
grid on;

% Loop through the data points
for i = 1:numPoints
    % Read a single data point
    d = textscan(fid, '%f', 1);
    a = d{:};
    
    % Update the plot
    plot(x, a, 'bo'); % Plot as blue circles
    drawnow; % Update the plot immediately
    
    % Pause for the real-time interval
    pause(interval);
    
    % Increment time
    x = x + dt;
end

% Close the file
fclose(fid);

Key Changes:

• drawnow: This function updates the figure window immediately, allowing for real-time plotting.
• Hold on: Keeps the current plot visible while adding new points.
• Figure Setup: Moved outside the loop for efficiency.
• Pause: Used to control the update interval to simulate real-time plotting.

This script reads data from `name.txt` and plots each point in real-time with a 0.004-second interval. Adjust `numPoints` based on your data file's length if needed.

I hope this helps!