Plotting two signals on one Graph using an array

Hi all,

I am using the code from the website below to plot a signal.

https://billwaa.wordpress.com/2013/07/10/matlab-real-time-serial-data-logger/#comment-365

I Modified the code as shown below so that I can display two signals on the same plot instead of just one signal. (Note that the comments with exclamation marks indicate the changes done). Why is it that only one signal is being displayed? How can I display both values of the array? Are there any other methods that I can use to achieve this? Any kind of help would be highly appreciated.

delete(instrfindall);             % if any port is already opened by MATLAB its gonna find and close it

%User Defined Properties
serialPort = 'COM5';            % define COM port #
plotTitle = 'Serial Data Log';  % plot title
xLabel = 'Elapsed Time (s)';    % x-axis label
yLabel = 'Data';                % y-axis label
plotGrid = 'on';                % 'off' to turn off grid
min = -1.5;                     % set y-min
max = 1.5;                      % set y-max
scrollWidth = 10;               % display period in plot, plot entire data log if <= 0

%Define Function Variables
time = 0;
data = 0;
count = 0;
%Set up Plot
plotGraph = plot(time,data,'-mo',...
                'LineWidth',1,...
                'MarkerEdgeColor','k',...
                'MarkerFaceColor',[.49 1 .63],...
                'MarkerSize',2);

title(plotTitle,'FontSize',25);
xlabel(xLabel,'FontSize',15);
ylabel(yLabel,'FontSize',15);
axis([0 10 min max]);
grid(plotGrid);
%Open Serial COM Port
s = serial(serialPort)
disp('Close Plot to End Session');
fopen(s);

tic
while ishandle(plotGraph) %Loop when Plot is Active

      dat = fscanf(s,'%f,%f');        % !!!!!!!!!!!!!!!!!!

      if(~isempty(dat) && isfloat(dat))    
          count = count + 1;  
          time(count) = toc;    %Extract Elapsed Time
          data_array(count,:) = dat'; % !!!!!!!!!!!!!!!!!!

          %Set Axis according to Scroll Width
          set(plotGraph,'XData',time(time > time(count)-scrollWidth),'YData',data_array(time > time(count)-scrollWidth));
          drawnow;

      end
  end
  %Close Serial COM Port and Delete useless Variables
      fclose(mbed);   %close connection (this should never be reached when using while(1), but included for completeness)
      delete (mbed)                             % deleting serial port object
      clear mbed                               
      clear all

Answer 1

[Star Strider]

I can’t run your code and I have difficulty following it.

See if the hold and drawnow functions (separately or together — you’ll have to experiment) will do what you want.

[John Smith]

@Srar Strider . Thanks for the reply. I tried both but neither is working. I now did my changes and the plots will be set on different figures. Now I have another small problem. How can I remove the values form the x-axis? From the forum I found that one should use 'XTick', [] , but were exactly should I place it please? I tried it as shown below but it did not work:

set(plotGraph,'XData',time(time > time(count)-scrollWidth),'XTick', [],'YData',data_array(time > time(count)-scrollWidth));

[Star Strider]

That looks correct, and it worked for me when I used it with a sample plot. I can’t determine what the problem may be.

[John Smith]

Am am getting the following error:

Error using set
Invalid property found.
Object Name: line
Property Name: 'XTick'.

Can it be that it is conflicting with the graph declarations at the beginning of the code?

[Star Strider]

You need to address the current axis handle, not the line handle, with that:

set(gca, 'XTick',[])

That should work.

[John Smith]

It worked, Thanks :)

[Star Strider]

My pleasure!

[John Smith]

Another small question. I am plotting multiple graphs (something similar as the code below), should I include drawnow below each plot or just one at the end? Thanks.

set(plotGraph1,'XData',time(time > time(count)-scrollWidth),'YData',data1(time > time(count)-scrollWidth));
axis(figure1,[time(count)-scrollWidth time(count) min max]);

set(plotGraph2,'XData',time(time > time(count)-scrollWidth),'YData',data2(time > time(count)-scrollWidth));
axis(figure2,[time(count)-scrollWidth time(count) min max]);

set(plotGraph3,'XData',time(time > time(count)-scrollWidth),'YData',data3(time > time(count)-scrollWidth));
axis(figure3,[time(count)-scrollWidth time(count) min max]);

[Star Strider]

If they are different figures or different subplots, include drawnow after the plot call in each one. That’s how I would do it.

If you want a fixed axis (using the axis function), put that just after the plot call:

function(#) OR subplot(#,#,#)
plot( ..., ...)
axis([xmin  xmax    ymin  ymax])
drawnow
... ANYTHING ELSE ...

This order of function calls has worked for me in the past when I’ve coded animated plots.

For example:

[X,Y] = meshgrid(linspace(-5, 5, 50));
fcn = @(x,y,k) k*x.^2 + y.^2;

v = [1:-0.05:-1;  -1:0.05:1];
for k1 = 1:2
    for k2 = v(k1,:)
        surfc(X, Y, fcn(X,Y,k2))
        axis([-5  5    -5  5    -30  50])
        drawnow
        pause(0.01)
    end
end