Updating the plot problem while using refreshdata

Hi!! I was having a problem on my code while using the refreshdata, and I was hoping for your help. I want to see the actual first peak and valley from my data, then update the plot after passing them until i reach the last value in my data. I tried first to just run the whole data, but I am already stuck with it and just keep getting the whole data, and was fast too. I was actually planning to use it for the succeeding codes that I already have and for a real-time signal analysis.

I am not used to Matlab coding too so bear with me please.

Here is the code I made

%raw data from XYZ direction
NormChest = readtable('Tidal/TV_500ml.csv');                   %%%get the raw data 
C = table2array(NormChest(:,1));                               
x = table2array(NormChest(:,2));
y = table2array(NormChest(:,4));
z = table2array(NormChest(:,6));
total = table2array(NormChest(:,8));
time = C(:,1);

%--------------------------------------------------------------------------
% get relative acceleration
x = x - mean(x);
y = y - mean(y);
z = z - mean(z);
total = total - mean(total);

% % plot for raw data
% figure (1)
% plot (time, x, time, y, time, z, time, total), legend('x','y','z','total'); axis tight; 
% title ("Subject 1 (500 mL)")

%--------------------------------------------------------------------------
%partial delay                  %Still having difficulty here  
x1 = time;     %trial
y1 = z;     %trial
h = plot (x1, y1);
h.XDataSource = 'x1';
h.YDataSource = 'y1';

for i = 0:20
    refreshdata (h, 'caller');
    drawnow;
end

% 
% 
% for i = 1:1:numel (time)
% 
%     % refreshdata;
% end

Answer 1

[Avni Agrawal]

Hi Stella,

I understand that you are trying to create a plot that updates in real-time, showing the first peak and valley of your data, and then updating the plot as you step through the data. The `refreshdata` function is used to update plots when the data source has changed, but in your case, you need to update the data source incrementally.

Here's a revised version of your code that will create an animated plot. This example uses a for-loop to simulate real-time data plotting by updating the plot with one data point at a time and then pausing briefly. This should give you the effect of the plot being drawn in real-time. Note that for large datasets, you may need to adjust the pause duration to control the speed of the animation.

% Read the data from the CSV file
NormChest = readtable('Tidal/TV_500ml.csv');

% Extract data from the table
time = NormChest{:, 1};
x = NormChest{:, 2} - mean(NormChest{:, 2});
y = NormChest{:, 4} - mean(NormChest{:, 4});
z = NormChest{:, 6} - mean(NormChest{:, 6});
total = NormChest{:, 8} - mean(NormChest{:, 8});

% Initialize the plot
figure(1);
h = plot(time(1), z(1), 'b'); % Start with the first data point
hold on; % Keep the plot for updating
xlabel('Time');
ylabel('Z-axis acceleration');
title('Subject 1 (500 mL) - Real-time Signal Analysis');
axis tight; % Set the axis limits to the range of the data

% Set the data source properties for dynamic updating
h.XDataSource = 'x1';
h.YDataSource = 'y1';

% Loop through the data to simulate real-time plotting
for i = 2:length(time)
    % Update the data source
    x1 = time(1:i);
    y1 = z(1:i);
    
    % Update the plot
    refreshdata(h, 'caller');
    drawnow;
    
    % Pause for a brief moment to simulate real-time data acquisition
    pause(0.01); % Adjust the pause duration as needed
end

hold off; % Release the plot

This code will create a figure and plot the first data point. Then, in the loop, it will incrementally add one data point at a time to the plot and refresh the figure with `refreshdata`. The `pause` function is used to slow down the loop to simulate real-time plotting. You can adjust the duration of the pause to match the speed of your actual data acquisition or desired visualization speed.

I hope this helps.

[Stella]

Thank you Avni!!

I tried your code and it was great! But I also tried multiplying the i of x1 and y1 to 500 for getting every 500 data point, but I get this error "Index exceeds the number of array elements. Index must not exceed 29993. time appears to be both a function and a variable. If this is unintentional, use 'clear time' to remove the variable 'time' from the workspace."

I tried fixing my i value, but it still shows that error. I also tried just using the "time" data, but it cuts the plot short and only a quarter of the data was shown in the plot. Is there a command that I can use to fix it?

% Read the data from the CSV file
NormChest = readtable('Tidal/TV_500ml.csv');

% Extract data from the table
time = NormChest{:, 1};
x = NormChest{:, 2} - mean(NormChest{:, 2});
y = NormChest{:, 4} - mean(NormChest{:, 4});
z = NormChest{:, 6} - mean(NormChest{:, 6});
total = NormChest{:, 8} - mean(NormChest{:, 8});

%design for low pass filter
fs = 1000; %sampling frequency
fc = 1; %cut-off frequency
order = 1;
[b1, a1] = butter (order, fc/(fs/2));

%design for high pass filter
fcv = 0.1;
orderv = 1;
[b2, a2] = butter (orderv, fcv*2/fs, "high");

%--------------------------------------------------------------------------
%Filtering
acc = z
acc = filtfilt (b1, a1, acc);

% Initialize the plot
figure(2);
h = plot(time(1), acc(1)); hold on;   % Start with the first data point (1)
xlabel('Time'); ylabel('y-axis acceleration'); axis tight;   
title('Subject 2 (1.5 L) - Real-time Signal Analysis');

h.XDataSource = 'x1';       % Set the data source properties for dynamic updating
h.YDataSource = 'y1';

for i = 2:length (time)
    % Update the data source
    x1 = time(1:i*500);
    y1 = acc(1:i*500);
  
    refreshdata(h, 'caller');
    drawnow;

    pause(0.001); % Can be adjusted 
end
hold off;