Function to plot real time signals (e.g. from COM-port) using matlab

matlab-real-time-plot.m

% plotnow - function to plot real time signals 
% (e.g. from COM-port) using matlab
% 
% arr - array of data. 
% fs - sampling frequency
% t_width - time range to be shown
% ymin and ymax - range in y-axe
% 
% Example usage:
% 
% com_port = serial('COM1', 'BaudRate', 9600)
% fopen(com_port)
% i=0
% max = 255
% a = []
% while(com_port.BytesAvailable > 0)
%     data = fread(com_port, 10);
%     new = (5 .* data / max).'
%     a = [a new]
%     plotnow(a, 1, 15, 0, 5);
%     i = i + 1;
%     pause(0.25);
% end
% 
% fclose(com_port) 
% 

function plotnow(arr, fs, t_width, ymin, ymax)
    dt = 1 / fs;
    len = length(arr);
    n_width = round(t_width * fs);
    if n_width >= len
        t_disp = 0:dt:(len-1)*dt;
        arr_disp = arr;
        xmin = 0;
        xmax = dt*n_width;
    else
        n_min = len - n_width;
        t_disp = n_min*dt:dt:len*dt;
        arr_disp = arr(n_min:len);
        xmin = n_min*dt;
        xmax = len*dt;
    end
    plot(t_disp, arr_disp);
    axis([xmin xmax ymin ymax]);
    drawnow;
end